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 Automotive
Brake
systems 7
Automotive brake systems
Classroom Manual

7
EDITION

Ken Pickerill

SE/Author/Author, Title, 5th Edition   ISBN -978-X-XXX-XXXXX-X ©2014 Designer: XXX

Text & Cover printer: Transcon-Beauceville   Binding: PB   Trim: 8.5" x 10.875"   CMYK
 CLASSROOM
MANUAL
For Automotive Brake Systems

64533_fm_hr_i-xx.indd 1 02/02/18 3:54 pm

64533_fm_hr_i-xx.indd 2 02/02/18 3:54 pm
 Classroom
Manual
For Automotive Brake Systems

SEVENTH EDITION

Ken Pickerill

Australia • Brazil • Mexico • Singapore • United Kingdom • United States

64533_fm_hr_i-xx.indd 3 02/02/18 3:54 pm

 Today’s Technician: Automotive Brake © 2019, 2015 Cengage Learning, Inc.
­Systems, Seventh Edition Unless otherwise noted, all content is © Cengage
Ken Pickerill
ALL RIGHTS RESERVED. No part of this work covered by the copyright herein
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Notice to the Reader

Publisher does not warrant or guarantee any of the products described herein or perform any independent analysis in connection with
any of the product information contained herein. Publisher does not assume, and expressly disclaims, any obligation to obtain and include
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Printed in the United States of America

Print Number: 01    Print Year: 2018

64533_fm_hr_i-xx.indd 4 02/02/18 3:54 pm

 Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Chapter 1 Brake System Fundamentals . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction 1 • Brake System Overview 2 • Trailer Brakes 13 • Summary 18 • Review
Questions 18

Chapter 2 Principles and Theories of Operation . . . . . . . . . . . . . . . 20

Introduction 20 • Brake Operation/Conventional System 21 • Brake System Energy 22 •
Braking Dynamics 24 • Friction Principles 25 • Energy and Work 31 • Newton’s Laws of
Motion 32 • Hydraulic Principles 33 • Vacuum and Air Pressure Principles 39 • Electrical
Principles 39 • Summary 41 • Review Questions 42

Chapter 3 Related Systems: Tires, Wheels, Bearings, and

­Suspensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Introduction 44 • Tire Fundamentals 45 • Run-Flat Tires 51 • Tire Pressure Monitoring
System 53 • Wheel Fundamentals 54 • Wheel Bearings 56 • Wheel Alignment
Fundamentals 58 • Effects on Braking Performance 62 • Performance Tires, Wheels, and
Alignment 63 • Summary 66 • Review Questions 66

Chapter 4 Master Cylinders and Brake Fluid . . . . . . . . . . . . . . . . . . 68

Introduction 68 • Hydraulic Brake Fluid 68 • Brake Pedal and Pushrod 74 • Split Hydraulic
Systems 75 • Dual-Piston Master Cylinder Construction and Operation 78 • Fast-Fill and
Quick Take-Up Master Cylinders 88 • Central-Valve Master Cylinders 91 • Summary 92 •
Review Questions 93

Chapter 5 Hydraulic Lines, Valves, and Switches . . . . . . . . . . . . . . . 95

Introduction 95 • Brake Lines and Hoses 95 • Brake Electrical Warning System 112 •
Summary 120 • Review Questions 120

Chapter 6 Power Brake Systems . . . . . . . . . . . . . . . . . . . . . . . . . . 122

Introduction 122 • Increasing Brake Force Input 122 • Vacuum Principles 123 • Vacuum and
Air Systems for Power Boosters 125 • Vacuum Power Boosters 128 • Hydraulically Assisted
Power Brakes 137 • Summary 145 • Review Questions 146

Chapter 7 Disc Brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

Introduction 148 • Disc Brake Advantages and Disadvantages 149 • Disc Brake Construction
154 • Caliper Construction and Operation 167 • Types of Disc Brakes 172 • Rear-Wheel
Disc Brakes 177 • Performance Disc Brakes 177 • Summary 179 • Review Questions 179

Chapter 8 Drum Brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

Introduction 182 • Drum Brake Construction and Operation 186 • Drum Brake
Designs 202 • Summary 208 • Review Questions 208

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 vi

Chapter 9 Parking Brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

Introduction 210 • Parking Brake Operation 210 • Parking Brake Controls—Levers and
Pedals 212 • Warning Lamps 214 • Parking Brake Linkage 215 • Electrical Parking Brake
Systems 220 • Rear Disc Parking Brakes 221 • Summary 224 • Review Questions 224

Chapter 10 Electrical Braking Systems . . . . . . . . . . . . . . . . . . . . . 227

Introduction 227 • Common Components and Terms 227 • Antilock Brake System and
Vehicle Control 232 • Abs Types and General Operations 232 • Abs Brands 234 • Abs
Components 235 • Communications 240 • Traction Control System 241 • Delphi Dbc-7
Abs 242 • Summary 247 • Review Questions 247

Chapter 11 Advanced Braking Systems . . . . . . . . . . . . . . . . . . . . . 250

Introduction 250 • Stability Control Systems 250 • Stability Control Hardware 257
• Active Braking Systems 262 • Regenerative Braking Systems 263 • Summary 264 •
Review Questions 264

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287

64533_fm_hr_i-xx.indd 6 02/02/18 3:54 pm

 PREFACE

The Today’s Technician™ series features textbooks and digital learning solutions that cover
all mechanical and electrical systems of automobiles and light trucks. The content cor-
responds to the 2017 ASE Education Foundation program accreditation requirements.
They are specifically correlated to the Task Lists contained in each level of program
accreditation; Maintenance and Light Repair (MLR), Automotive Service Technology
(AST), and Master Service Technology (MAST).
Additional titles include remedial skills and theories common to all of the certification
areas and advanced or specific subject areas that reflect the latest technological trends.
Today’s Technician: Automotive Electricity & Electronics, 7e is designed to give students a
chance to develop the same skills and gain the same knowledge that today’s successful
technician has. This edition also reflects the most recent changes in the guidelines estab-
lished by the ASE Education Foundation.
The purpose of the ASE Education Foundation program accreditation is to evaluate
technician training programs against standards developed by the automotive industry and
recommend qualifying programs for accreditation. Programs can earn accreditation upon
the recommendation of ASE Education Foundation. These national standards reflect the
skills that students must master. ASE Education Foundation accreditation ensures that
certified training programs meet or exceed industry-recognized, uniform standards of
excellence.

HIGHLIGHTS OF THIS NEW EDITION—CLASSROOM MANUAL

The text and figures of this edition are updated to show modern brake technology and its
applications, including the integration of stability control and active braking systems. The
Classroom Manual covers the complete mechanical-hydraulic automotive braking theo-
ries. It introduces the reader to basic brake systems as well as advanced electronics utilized
in stability control systems. The following chapters cover basic brake physics theories:
discussion of newer components and materials, including a section on electric parking
brakes, and any braking functions required for passenger cars and light trucks. The reader
is introduced to fundamental information on trailer brakes, DOT requirements for trailer
brakes, and a brief introduction to air brakes. Chapter 10, Electrical Braking Systems
(EBS), simplifies the discussion on traditional antilock brake systems (ABS) while retaining
the information for a complete understanding of ABS. Included in this chapter is a detailed
discussion of electro-hydraulic brakes including the Teves Mk60/70, Delphi DBC-7, and
the newer Bosch 9.0 are introduced in chapter 11, Advanced Braking Systems goes more
into depth on stability control and its relationship to traction control and ABS systems.
This chapter also explains some of the ancillary systems that make stability control work
more effectively, such as electro-hydraulic and fully electric steering and tire pressure
monitoring systems. The very latest technologies, such as active braking and intelligent
cruise control systems, are introduced. Lastly, the chapter examines regenerative braking
systems in use on the latest hybrid vehicles in production today. The Classroom Manual
guides the reader from traditional hydraulic brake to the brake system of the future.

vii

64533_fm_hr_i-xx.indd 7 02/02/18 3:54 pm

 viii

HIGHLIGHTS OF THIS NEW EDITION—SHOP MANUAL

Safety information remains in the first chapter of the Shop Manual, placing this critical
subject next to the tasks to be accomplished. Chapter 2, Brake Service Tools and
Equipment, covers basic tools with more information on brake special tools and equip-
ment. Figures and technical information have been added to cover the use of common
shop tools such as on-car brake lathes. Some of the safety information that is pertinent to
a particular piece of equipment is still in the chapter, so safety issues are presented just
prior to the operation of the equipment. In keeping with typical shop diagnostic proce-
dures and curriculum sequence, Chapter 3 retains the information on related systems that
may have a direct impact on the braking system. Updated information on diagnosing
electric parking brakes and electric braking systems has been added to this edition. To
clarify the diagnosis and repair procedures for electric braking, three major ABS/TCS
brands, Delphi DBC-7 and Bosch ABS 9.0 and Teves Mk 60/70, are retained for discussion
instead of an individual discussion on all industry ABS offerings. This helps the reader
better understand the technical diagnosing and repairing for all ABS/ TCS. This edition
of the Shop Manual will guide the student/technician through all the basic tasks in brake
system repair and presents a look into the near-term future of electric brakes and vehicle
stability systems. The Shop Manual has several additions in the Advanced Braking Systems
chapter, Chapter 11. This chapter deals with the diagnosis and repair of stability control
systems and the surrounding technologies, such as electric steering, tire pressure monitor-
ing systems, active braking, and intelligent cruise control.

64533_fm_hr_i-xx.indd 8 02/02/18 3:54 pm

 ix

CLASSROOM MANUAL
Features of the Classroom Manual include the following:

C h a pT eR 1
BRake SyST
em FUNDam
eNTalS

Cognitive Objectives Upon comple

tion and review of
this chapter, you
■List and descr should be able
These objectives outline the basic parts of
ibe the opera
a brake system
tion of the
■ Descr
to:
. ibe the use of
chapter’s contents and identify ■ Descr
ibe the opera
system during tion of the bra
ke
to dir
fluid.
ec t
valves
and control the and lines
hydraulic
and after peda
what students should know and application.
■ Discus
l ■ Discus
s the pu rpo se of brake po
s the increasin boosters and
be able to do upon completion of brakes instea g use of disc the parking bra wer
d of drum bra ■ Discus ke.
kes. s the general
operation of ele
the chapter. Each topic is divided ■ Descr
system.
ibe a typical bra
ke hydraulic
tronic and act
■ Discus
ive braking sys
tem s.
c-
s the general
into small units to promote easier Terms To know
brakes and air
brakes.
op era tio n of trailer

understanding and learning. Active braking

Actuators Friction
Fulcrum Service brakes
Air brakes
Terms to Know List Antilock brake
system (ABS)
Lateral acccel
Leverage
erometer
Steering whee
sensor
l position
Automatic rid
e control Stroke sensor
A list of key terms appears in (ARC) Lockup
Stroke simula
Bulkhead Master cylind tor
the beginning of the chapter. Caliper Negative whee
er
Traction-contro
l system (TCS)
l slip
Students will see these terms Disc brake Parking brakes Vehicle stability
(VSC)
control
Positive whee
discussed in the chapter. Drum brake
Force Pressure
l spin Wheel cylinder

Definitions can also be found in Regenerative

braking
Wheel speed
sensors
Yaw
the Glossary at the end of the INTRODUCT
ION
age
manual. The brake system
is one of the mo eel. The sa
les of lever
me princip pad applied
ake
functiteonr 1s: st importawo nt -spoked wh d the force of the br ph and little
entem
ap e on a odsys s oncrea se to 20 m
llations in a vehicle. 10 mph
Ch
4 a solid tir s fou meant that early
1. It must slow to the outside ofodern brake pedal instaed well with speeds ofeuItmha atic tiresr basic
a mo vin
wo rkg in m
veh icle. ese br ak es wo rk nd ) an d pn
r
2. It must bringthat tire. Th and beyo using eithe
a veh
the solid ce (30 mph iles were
3. It must hold to ffic.icle to a sto s.
gher p. rman ived on automobiletie
perfo
th centur
y, automob es. A few internal-
veh Hista
a tra re short-l drum brak ontracting brakes
4. It allows dir wagoicle n braktio wery
es na whenst sto ca
de pp de of the twen
xp an din g l-c
ectional con of the fir ed internal-e les. Externa driveline
By thetro enlddu
rinngg ma
band brakes . or e early motor vehic um located on the
xim um m dr tighten
If the brake sys external-contracti brakes we
re tri ed onbrasokin
lg.wrapped
around a and linkage
nter; levers famous Model T
tem do es nd ate ria e ce
expand nolin
injured or killed ing ba t op ctio n m at th Ford’s
era
wi te
th fri
pro pe on e end or es on
in anhaaccveide
ed
nt.ndTechnic rlych, or ed at
the drice rvice br ak
forver
a ba is an anedsepa mission.
skilled expforc The basnd . Th ssethnge ers
transcou er braking
erte sthabe
tion is the wee
t
causeorthe the wheels. eian
on wo whforo ser
brak vicing
e the a drke um inside ectiven eslds whbeen highni
ofFric rk the th drum applied to bra sys eir eff cal servo
lose thtem
und do
e band aro ynt
bet n
resthe bra
ists mo tionke
sys tem canng sav
baendlive s. must be hig the mecha
t hly nd
es of two by th
pre sentingle co
g the ra cti In
ex thi
ter na l,
s chapter,u will lea rn ab ou
internal ba
the surfac s of matter. were a sin bas r incep ternal or brakes, yo wesesta n with an brake tends
objects or form es, eitichecon tsdyandrdum par rvrt outio
o ac r stu dy
Band brak hen yo u stu ts of de
to velop
all brake sys an exter nal band
associ-
ed ed. W ry dif fic ult ac tio n tem
on s. ob lem s
force is ne s. It is ve ed. Servo d. Other pr ternal
ke is a bra
ke brake shoe e force is thus need drum spee on with ex too
A drum bra action of and high s of fricti
tion is higher brak at high brake forces e and los ated and expanded d
in which fric brake brake, and ter damag
Margin Notes duce
by br ak e gr ab t an d wa um ov erhe an d re
generated g against e dir k if the dr
shoes rub bin to make th nd brakes include akes to loc nd and drum ov
erheating
surface of
a
ated with
ba of these br ba
the stan- 1
64533_ch01_h the inside
attached to an d th e tendency als o su ffer from be ca m e
r_001-019.ind
d 1 brake drum bands brakes rum brak
es 50s,
The most important terms to know are the wheel. much. In
ternal band
rce. ernal-exp
oe-and-d
anding sh parking brakes until
the late 19
braking fo brakes evolved, int es were used 1920s.
as
highlighted and defined in the margin. Common As dr um
nal-contra
dard. Exter as service brakes
cting ba nd br ak
were over
by the lat
e
nal-expan
s were the
ding shoe linkage
ys with inter lev ers and 1/31/18 10:3
9 AM
trade jargon also appears in the margin and but th eir da
ak es .
1920s, dr
um br ak
By the mid- akes were operate 21 Duesenberg M
es
d mecha
nica lly by re among
odel A we lower-
pe ar on
Drum Br drum br the 19 d to ap rd
gives some of the common terms used for le. Ea rly
general ru . Expensive luxury brakes . Hydraulic
3)
cars su ch as
brak es sta
, which be
rte
came the
Plymou
odel year.
th . Fo

(Figure 1- aulic drum r’s Light Six e 1938 m

have hydr th Chrysle l brakes through th
components. This helps students understand the first to the mid-1920s wi
in ed mec ha ni ca
priced cars wever, us
mpany, ho
and speak the language of the trade, especially Motor Co
asons for
the increa
sed use of
) The four
tw o major re lly-applied ones: (1 e same time
when conversing with an experienced technician. aUThOR
’S NOTe
pli ed
Ther
br
e we re
the mecha
nica
akes over me amount of brak -adjustment to m
ing force
at th
ake the
ally ap ply the sa constant
re s the
hydraulic emed to ap s required almost actical wa
ne ve r se ge ak es we re ever pr
brakes e br ak e linka m ec ha nical br gh sp ee ds.
) th on at hi
because (2 e only reas be traveled
rk at all. Th ugh and couldn't
brake wo ro
ads were e flexible
fact that ro ger than th
made stron rred with greater
es could be occu hydrau-
ed wi th drum brak kage problems that ter. W ith
s us
brake shoe ns. This eliminated
brea and fas most cars
powerful
The rigid ake de sig m ob iles got more br ak ing system for andards
rlier br as auto ndard y St
hicle Safet ade front
bands of ea s that were required es remained the sta Motor Ve
ce
braking for four-wheel drum br
ak of Federal rmance tests that m ntury,
e coming ce
lic actuati
on,
lat e 19 60 s. With th pa ss specific perfo of the twenty-first
iddle and d to g s.
into the m systems ha Even at the beginnin cars and light truck
in 19 67, brake 19 70 s. m any of
(FMVSS)
10 5
rule in th e eels of aft brakes
the general the rear wh from aircr g pressure
disc brakes still used on developed in
r, dr um brakes are di sc br akes were akes work by apply wheel hub
howe ve ive c br e
: A braking n automot “spot” brakes, dis hed to th
Disc Brakes forces two es. Moder lly as rotor attac
Disc Brak n origina a spinning
ar II. Know e sides of
t
system tha
on opposite World W e pads on opposit
brake pads nning rotor
ak
sides of a spi
vehicle to two br
to stop the 10:39 AM
1/31/18

9.indd 4
1_hr_001-01
64533_ch0

64533_fm_hr_i-xx.indd 9 02/02/18 3:54 pm

 x

ons 45
ings, and Suspensi
Tires, Wheels, Bear
Related Systems:
in proper
lems if they are not
create braking prob e systems and the
e components can ionships between brak
springs. Any of thes ines the key relat
chapter outl
working order. This
related systems of whe
els, tires, wheel bear
ings, and suspensions.
Cross-References to the
tIre Fundamen
talS
of weight, size, and
per- Shop Manual
Shop Manual
many vehicle factors
neered in relation to tread design of the
tires page 98
Brake systems are engi
formance . Amo ng thes e factors are the cons
ion
truction, size, and
expected to be avai lable betw een the tires and the
shou ld be
References to the appropriate page
tract ion or frict at all four whe els
and the amount of
road. For the best and
most reliable brake
performance, tires
and tread pattern.
in the Shop Manual appear whenever
truc tion , size,
identical in cons
mendations on
necessary. Although the chapters of the
carmakers’ recom information placard
since 1968 have a tire
Most passenger cars
and light trucks built
or insid e the glove compart
ment (Figure 3-1).
The tire informa-
any recommended
two manuals are synchronized, material
door pilla r, tire size and
a door, on a inal equipment
tion placard lists the
manufacturer’s orig
lists the recommende
d cold front and rear
inflation pressures,
and
are engi- Gross vehicle weight covered in other chapters of the Shop
optional sizes. It also WR). Brake systems rating (GVWR) is the
cle weight rating (GV
maximum front and
rear gros
t efficiently
s vehi
with the tire sizes and pressure s liste d
the front and
on the plac
rear
ard.
of som e
total weight of a vehicl
plus its maximum rated
e
Manual may be fundamental to the topic
neered to work mos rent sized whe els and tires at
ance sports payload, including pas-
A few carm aker s insta ll diffe
tice is reserved for
a small percenta ge of high -per form
on the road are orig
inally senge rs and full fuel
discussed in the Classroom Manual.
vehicles, but this prac percent of the vehicles
tank.
911. More than 99 turers may
cars like the Porsche Although manufac
tires of the sam e size at each corner. r than the fron t orig inal
fitted with wheels and tire sizes at the rear that are large to brak ing
two optional tion can lead
recommend one or aker’s recommenda
variation from the carm systems.
equipment size, a large with other vehicle uce
ter 2lems, as well as problems
approb diam eters from front to rear may prod
Ch e in tire than thos e t
22
For example, an extr sTeM
eme differenc eR GY s much largerysi andalsthe concep
sY eleN
spee d sensors of ABSs. Tireor “laspee ws ” of phnsor cs,sign s in
unequal speeBR aK
d sign alse from the whe
ucea inac
few ncipl
cura
pri es
te vehi cle d-se
y to do rk anrd come l
wolarge
er may prod
ing to ab ilit are ctr ica
the vehi cles mak
work accord if all four tires
y is sthe energy, and
ele
recommendedl by brake systemrol mod ule.phThis
ysical scieen
sam ce. En
prob lem ergexist
energy, heat
to the PCM of
Al
or the ABS cont basic par’s rt of
energtion y, mes. chanical s.
y is aufac
ergman recomml enda otive system To slow and stop a
or smaller than
enthe
ilia r for ms : chemica us forms in all autom
ture
an oth er.
many fam most obvio energy to y through
among the of physical to heat energ er, they
energy are s one form y of motion anoth
A brake sys
tem convert
an ge the kinetic energ e form of energy to
kes ch change on
g veh icle, the bra ytion. When the brakes or resis energ y.
amoBItvinoF hIStor lot of using tance by drivers to using
is the
Kinetic energy ical ion of fric of rel easaing
was
Author’s Notes
plicat
the apwere uced in theres 70s, ultthere have enough
han
energy of mec . When radial tiresdo ing
firstrk.
wo Work is the
introd
“feels funny when driving” to “they don’t le
work or motion the new desig aren. Complaints ranged from from a brand-new vehic energy.
to remove radial tires stroy
resis-
rs even went so far as e toame ate or
crethis deard
die-h
air in them.” Some drive r chara cteristics ssiof the
ble
radia
at
tire overc
thil s timfile e ma
have ste r cylinder is
also
aUTh
tance: a much smoo
OR
ther
Two
and to install bias tires. 's and
majo
ride NOTe increIt
ased
co nv
is im
ert
po
fuel mileamge.onLowe
ed fro
“app earin g unde y of
tires
r-proto anoth
e formrinfla ted.
the
of
er.today
Th
” brake pedal is co mechani-
nverted int
to
o
This feature includes simple
of the
we ver
comm ents be
, it can tires
about the mechanical en erg
co nv erted back
eliminated most Ho
s happens:
one place thi y in the master cylind
erg
the
er bore. It is
later
explanations, stories, or examples of
hydraulic en
the wheels.
cal energy at complex topics. These are included
starts,
ergy, Mas
s, Weight
, and spee
d
rk or motio
n. When an
automobile
of kinetic en
ergy to help students understand difficult
Kinetic en chanical wo
y of me The amount e at the rat
y is at work.
Kinetic energ
y is the energ
decelerates
, and stops,
kinetic energ
vehicle’s ma
ss (weight),
speed, and concepts.
accelerates, nt is de ter mined by a ibe objects on
y mome ly to descr
at work at an changinisg.located on the driver door interchangeab same. Mass is a me
and lists a-
ed is
spe3-1 This placard can be used
on pressure. are not technically
eight” the asurement
which Figure
ass ” an d “winflati
cold ht is a me
ject. Weig
ed “m and
terms
The mend
recom tire size
, bu t the two terms up an ob ke sho e to a
of the Earth s that make m a steel bra
the surface of molecule l objects have mass, fro ing too deeply into the
measure of the number ss. Al out go t and
surement of
Mass is the Related Sys
an object y on that ma ressor. With springs.lec s in an objec re tems: Tires,
the inertia of the effect of gravit air in an air comp mb er of mo Anule y of these commo Wheels, Be
arings, and
ject and the
tter or its of to the nu ponents can1/31/18 9:44 AM
ma
draulic fluid
the working
or form of the greater ss of thaord t ober. create brakin Suspensions
resistance to also is quart of hy cs, it can be said that gre ate r the marel ate d sys jec t’s
Thigh
we is cha
t. pter outlines
the
g problems if 45
acceleration;
it
en ce of physi ule s are, the t is that ob tems ofthi wh of the key relationsh they are not
of sci mo lec an ob jec nk ing
eel s, tire s, ips bet in proper
molecu
ther_044-0 lar 45
67.indd
den sity
mo re co mplex the vit y on the mass of be un de rstood by the Ea rth .wheel bearings, and ween brake sys
tem
64533_ch03_h the gra d weight can the launch pad, on suspensions. s and the
an object. The effect of een mass an 2-2). Its
dense it is. ference betw out 1,000,000 pounds tIre
on
ss (Figure
The basic dif ighs ab y, it is weFu ightle
nd amentalS
shu ttle , which we tsi de the Earth’s gravit ha s a
spa ce it, ou Brake system but spe ed
ttle is in orb etic ensergarey,eng -
When the shu same, however. speed const ma
forte kin
itu nce. Am obgject canere
ine bedcal incurelation to ma
mass stays
the weight and y movingon these ny vehicle fac
mb ine d effects of e kin etic energy
of an
and the amount of tra factors are the construct tors of weigh
t, size, and per
Th e co n weigh t. Th road. For the ctio n or friction ion, size, and -
r effect tha simple: bes expected to be tread design
much greate formula, which is quite identical in con t and most reliable brake available bet
ween the tire
of the tires Shop Manual
wi th thi s struction, siz performance s and the page 98
lated e, and tread pat , tire s at all four wh
carmakers’ ter n. eel s should be
2
mv 5 Ek recommen
Most passen dations
29.9 ger cars and
light trucks bu
a door, on a do ilt since 1968
or pillar, or ins have a tire inf
wh ere tio n placard lists ide the glove com ormation pla
in po unds optional sizes. the manufacturer’s origin partment (Fi
gure 3-1). Th card on
eight) It also lists the al equipment e tire inform
m 5 mass (w miles pe r ho ur ma xim um front and rea rec om me nded cold fro tire size and
any recomme a-
(sp eed ) in neered to wo r gro ss vehicle we nt and nded
v 5 velocity rear inflation
foot-pound
s rk most
A few carma pheffi ciently wit 2,000 ight rating (GVWR).
ighhs the
pressures, and
c energy in ). One we Brake system
Ek 5 kineti veh icle pe r ho ur ker
(m s ins tall dif fer
tire sizes and
pre ssu res s are eng i-
30 miles s, but this practic ent sized wh listed on the Gross vehicle
traveling at car e is reserved eels and placard. weight
o cars, both pounds (Figu like).the Porsch
res 2-3 for a small per tires at the front and rea rating (GVWR)
Consider tw e 911. More r of some is the
igh s 4,0 00 fitt ed wit tha n centage of hig total weight of
other we h wheels and 99 percent of h-performanc a
plus its maximu vehicle
pounds; the recommend tire s of the veh icles on the roa e spo rts
one or two opt the same size at each cor
m rated
d are payload, inclu
equipment siz ional tire sizes ner. Although originally ding
sengers and full pas-
e, a large variati at the rear tha manufacturers fuel
problems, as on from the car areAMlarger tha
1/31/18 t9:42 may tank.
well as proble n the front ori
For example, ms with other maker’s recommendation ginal
veh icle systems. can lead to brakin
unequal speed an extreme difference in g
sig tire diameter
recommended nals from the wheel speed s from front
to rea
by the vehicle sensors of AB
to the PCM or ma Ss. Tires much r may produce
the ABS contro ker may produce inaccu
d 22
r_020-043.ind
64533_ch02_h larger than tho
or smaller tha l module. Th rate vehicle spe se
n the manufac is same proble ed-sensor sig
turer’s recom m exists if all nals
A Bit of History mendations. four tires are
larger

a BIt oF
This feature gives the student a sense of the evolution When radial tire
s
hIStory
the new design. were first introduced in the
70s, there was
of the automobile. This feature not only contains and to install
Com
air in them.” Som plaints ranged from “fee
e drivers even
went so far as
ls funny when
a lot of resista
driving” to “the
nce by drivers
to
y don’t have eno using
bias tires. Two
major characteri to remove radial tires from
nice-to-know information, but also should spark some tance: a much
eliminated mo
smoother ride
and
stics of the rad
st of the comme increased fuel mileage. Low
ial tire overcame
a brand-new veh
ugh
icle
this die-hard resi
nts about the er-profile tires s-
interest in the subject matter. tires “appearing of
underinflated.” today have also

Figure 3-1 This

recommended placard is located on the driv
tire size and cold er doo
inflation pressure r and lists
.

64533_ch03_h
r_044-067.ind
d 45

1/31/18 9:44
AM

64533_fm_hr_i-xx.indd 10 02/02/18 3:54 pm

 xi

92 Chapter 4

In most instances, only one dual-piston cylinder is used with some type of split sys-
tem. However, some race crews opt for two identical single-piston master cylinders. The
two master cylinders act like a split hydraulic system in that one master cylinder serves
the front wheels, whereas the other serves the rear wheels. The master cylinders are
applied by one brake pedal acting through a balance bar between the pedal lever and the
two push-rods. Some race units are equipped with a brake power booster, and others are
not. In this case, it is more an issue of weight than of driver endurance.
Of primary importance to race vehicle braking is the type of brake fluid used. On short
tracks with a lot of braking, the boiling point of the fluid can be reached quickly and may
be sustained for long periods. Brake fluids developed for racing purposes generally have
the same chemical properties as conventional fluids, but they have much higher boiling
points. Castrol offers a blend of polyglycol ester of dimethyl silane, ethylene polyglycols,
and oxidation inhibitors. This blend has a dry boiling point of 4508F(2328C) and helps
prevent fluid contamination during operation. Another brand, GS610, offers a fluid with
a dry boiling point of 6108F(3218C). There are several manufacturers and suppliers of rac-
ing brake components. Brembo is one of the larger manufacturers of racing components,
and some of its products are now being installed on some production performance
vehicles.

Summary
sUMMARY
Each chapter concludes with summary statements ■Brake fluid specifications are defined by SAE hydraulic systems. Each of the two pistons in the
that contain the important topics of the chapter. ■
Standard J1703 and FMVSS 116.
Fluids are assigned DOT numbers: DOT 3, DOT 4,
master cylinder has a cup, a return spring, and a
seal.
These are designed to help the reader review the DOT 5, DOT 3/4, and DOT 5.1. ■ During application, the piston and cup force fluid
■ Always use fluid with the DOT number recom- ahead of the piston to activate the brakes.
contents. mended by the specific carmaker. ■ During release, the return spring returns the
■ Never use DOT 5 fluid in an ABS or mix with any piston.
other brake fluid. ■ Fluid from the reservoir flows from the reservoir
■ HSMO fluids are very rare and should never be through the replenishing port around the piston
used in brake systems designed for DOT fluids. cup.
■ The brake pedal assembly is a lever that increases ■ Excess fluid in front of the piston flows back into
pedal force to the master cylinder. the reservoir through the vent 93
uid ports.
Brake Fl
■ The brake pedal lever is attached to a pushrod, ■ Quickyltake-up inders an ordfast-fill master cylinders have a
M aster C
which transmits force to the master cylinder pistons. step bore, which is a larger diameter bore for the
■ A front-to-rear split hydraulic system has two mas- rear section of the primary piston.
ter cylinder circuits. One is connected to the front ■ Quick take-up master cylinders have a valve that
s: a
partlow-pressure
brakes and the other to the rear brakes. provides rapid o maiofn the
filling spool area
■ A diagonally split hydraulic system is one in which r cythe der has tw
linprimary ______ _.
T IO N s T he masteof d a __piston
______from the reservoir.
s
Review Questions REVIE W Q oneU Emaster cylinder circuit is connected to the left ____
front and right rear brakes and the other circuit is
8.
__ __
■ __ _
the headsr of
an
____ ABS master cylinders
Some
caps
ar e
coversto reduce
theorpistons
have
ve nt ed
______piston
to valves in
check
_ as and pedal
ter cylinde and ________
_____ wear.
connected to the right front m- rear brakes.
and left
is not reco 9. All mas vibration ________ cup rvoir.
Short-answer essay, fill in the blank, and Essay ■ The master T 5 br ak e
cylinder flu id
has two main parts: a reser- prev ■ Portless en t a __
level drop
master th e re se
s in cylinders do not use der aisreplenish-
n why DO aancylinder ufacturebody. r. the fluid ing or vent port. e cylin
thflow
1. Explai voiranand id is rear of
theFluid can between the reser-
multiple-choice questions follow each by y m
mende■d The reservoir
the bo ili ngcanpobe brake flu
int aofseparate piece or cast as one pist voir
on semthe
asand bly at areast ahead
on , an thethe
d of
at the
onemaster
___ piston
.
cylinder
ai n w hy 5 10. The __ __ __ __ _ pi
__ __ __ __
chapter. These questions are designed 2. Expl piece
import ■ an
with the cylinder.
At.dual-piston a go od
master ea to mix
idcylinder
DOT
has two separate pis- of
pistons by means of a valve machined into the
the ______ cylinder is the ____
e
master
th cylinder pistons when the master cylinder
is not front
n why it DOT 4. for two independent
to accurately assess the student’s 3. Explai tonsDproviding
s w ith OT 3 and
pressure
e flu id contamin
ation is at rest.
fluid gn of brak
competence in the stated objectives at e a sure si ch an ge s
4. Describ eral oil. free-play
is Choice cy lin de r
with min dal linkage Multiple e m as te r da l to
brake pe A says th l fo rce on th e pe
the beginning of the chapter. 5. Expl ai n w hy
1. Te ch ni ci an
m echa ni
ca
ni ci an B to
says th is
ne ce ssar y. dr au lic system. th e dr iv er ’s re . Te ch
92hy
n the split site master cylinde d how it is
r. pres su d ba ck
hy dr au lic es su re is ch an ge br akes . W ho is
64533_ch04_hr_068-094.indd 1/31/18 9:48 AM
6. Explai an
e a compo cup seal pr
hy dr au lic l fo rce at th e w he
el
7. Describ a master cylinder ca
8. Describ
e
of the m echa ni and B
. bo tto m ec t? C . Both A
used rts in the do co rr
er A nor
B
W ha t are the po servoir, and what A on ly D . N ei th
9. linder re A.
master cy -u p m aster on ly t flu id for a
ke B ng the ri gh
they do? a quick ta B.
ys choosi the simple idea th
at if
ntage of cian A sa
n the adva 2. Techni d on d DOT
10. Explai c ve hi cle is base t be better, an man-
cylin de r. spec ifi T4 m us hicle
good, DO ys most ve
DOT 3 is . Technician B sa Who is correct?
5 better still mmend DOT 4.
e Bla nk s
cylinder
is reco A and B
Fill in th p master sa ufacturers C. Both rB
ill or qu ick take-u design that create A on ly . N ei ther A no
-f al bore . D
1. A fast by the du _______
A
of brake
identified _____ or ________ B. B on ly
y boiling
po in t
con-
__
________ _____ of the castin
g.
cian A sa
ys the dr of new, un -
ng point glycol flu
________
__
e
ne-
polyalkyle ___ for 3. Techni e minimum boili says poly
id s ar __ id is th ni ci an B do
4 flu ____ flu
fluid. Tech they
and DOT d ______ eans that
2. DOT 3 er mixtures, calle taminated oscopic, which m e air. Who is
glycol-eth gr r from th
ids are hy at er va po
ids rb w
short. DOT 4 flu air, not abso A and B
OT 3 and from the correct? C. Both
e both D _______
3. Becaus _______ ________ ed . er A nor
B
________ containers tightly
ca pp
A . A only D. Neith
ke ep tly un de r ly bo ili ng
always _____ sligh ake B. B on ture
-tempera ake fluid
________ slightly spongy br ys a high
e fluid __ a cian A sa ent that br id also
4. Silicon which can cause 4. Techni e only requirem br ak e flu
re , th ys
pressu point is cian B sa d must
pedal feel
. ________
_ t. Techni oration an
a ve ry ______ must mee freezing and evap w temperatures.
flu id s ha ve us t re sist te st s at lo
yc ol m ity
5. Polygl ific viscos
________
___ pass spec ect?
shelf life. -to- ____ rr C. Both
A and B
__ _______ st split Who is co rB
__ __
6. The __ split system is th
e ol de
. A on ly D . N ei ther A no
A
hydraulic __ _ B on ly
____ __ B.
system. a ______
cars have
te-model
7. Most la aulic system.
split hydr

9:48 AM
1/31/18

93
094.indd
4_hr_068-
64533_ch0

64533_fm_hr_i-xx.indd 11 02/02/18 3:54 pm

 xii

Shop Manual
To stress the importance of safe work habits, the Shop Manual also dedicates one full
chapter to safety. Other important features of this manual include:

1
C h a p Te R
feTy
BRake Sa

Basic Tools Lists

Basic Too ls
s chapter, you
should be ab
le to:
ts for workin
g s or
Each chapter begins with
Performance-Based Upon comple
tio n
ne
and
ed
review of thi
an d methods
■ Lis t the
with brake
saf ety requiremen
fluid.
asb est os
Safety glasse

Res
goggles
pira tor
a list of the basic tools
the of
Objectives ■ Explain
for maintain
area.
ing a safe
working ■ Describe
materials.
the hazards

ety concerns
with sol-
Vacuum with
filter
HEPA
needed to perform the
ety issues saf sys tem
These objectives define the ■ List and
discuss som
h vehicle op
e saf
eration in the
■ Expla in
vents and oth
the
er chemical
s.
ns of the
We t-cl ean
Carbon monox
ide tasks included in the
dealing wit ge neral functio of ven t system
contents of the chapter and shop.
e of the co
mmon sen se ■ Expla in
safety and
the
en viro nm en tal agen
Canada.
cie s
Fire exti ngu ish er(s) chapter.
■ Explain som wer States and
rking with po the United hazardous
rules for wo of
define what the student should equipment.
and equipme
nt in ■ Discuss the
pri nci
tions.
ple s
Master Cy
per clothing communica rns linder an
safety conce d Brake
have learned on completion of ■ Wear pro
a shop. p to remove
■ Dis cus
oc
s some of the ck brake and air
iat ed with antilo
Fluid Se
rvice
135
first aid ste ass
the chapter. ■ Ex pla in
chemical
the
s fro m the eyes.
governmen
t
bag sys tem s.
hnician tra inin g an d
purpose for ■ Discuss tec
■ Explain the
and .
rformance certification
of brake pe
regulations
standards.
tion (OSHA)
ow Administra
Terms To kn tal Canada
Environmen n Ph osgene
Asbestos tal Protectio tal inflatable
Environmen Supplemen
Agency (EP
A) tem (SIRS)
Asbestosis restraint sys
r for
Figure 4-2
n Pro
Ch ced ures (EP) roe thylene
nte ctio eck
Tetrachlo
Canadian Ce Health Extra ing stop lamp
al BR tor Vehic le op era tion. roethane
Occupation AK Federal Mo 1,1,1-Trichlo
(CCOHS) E pEDAl Mndards (FMVSS)
and Safety Safety Sta EChAniC et Trichloroethy
lene
Ch
mo noxide ecking the brak ial safety data she Al Ch E zardous
WoC
Ca rbo n shooting. Maeterpedal mec rkpKlac e Ha
hydroc arb on W hether(M ha nical oper ormation
Chlorinated test, check th yoSD S)
u do Materials Inf
ts ese points ation it as pa
al Sa and ation is an im
fetofy th
rt t po
sol ven ■ Ch Occupof pedal op e brake sy Sh ee rta nt part of Classroom
ec k fo eration: ste m road test brake tro Manual
t of (w r frictio Health page 74
Departmen T)e engi n and noise by pr
ith th
(DO
or during
a system
uble-
ort ati on ne running es sin leak
Transp return s with no for powe g and re
Move lag or no r brakes). leasing the brake
■
the brake ise Be da bu pe t also Special To
peda ov l, severaan
. sure the is wearing
peCT
INTRO■DU
Chec
IO
dal m N peda
ounting pa l from side ttoonsid
rts. olves no
k stop lam injpury
lye.wh
inv Exce
an
at the technici is lifmon
e here
eestec ooici
smhn
ld adssvan
l times
thly and
side mov keeping the shop
ivetag
Coworker
ols
Special Tools
Htectioancofrom operataiosaf e. The twofo d
uipment anement ce
Personal pro avepin
eakee g therkwo
making and ch tim
sto
tin g him
pligh
wo er rk
e fitby
sel is re we ari
are n by
check th
ng pe rso
at
leased (F ployee
ig
thna
e
depr
lams ps
or
singtioanndeq
estec
l pro
vishtitoears
lig
re
sta nd
lea sinag go
theme
uip br ntetha
ak
indicaavo
od chan of s wo
te iding
t will provid
rn
e Lists
is protec ha t. It is im
all the po oth er emure 4-2), in practices tim ch andeeqth e
pedal seve
ral times
vee,tothe n 4 rtantdis s tho se clu ding the pe da l is presse
clean and saf
Aorpinj E R
ha
T ury. This chignition in ru
ve th e apt
R er tocunosse
te th at som th ird or center d an d go off
.
1 Whenever a special
accCideh
linDE viCE
n before e vehicles equipp
nts —high
. ed with lig -mounted—
ER CY luiD SER
rsonal safety the brake
overallpand pe T lamps wi hting mod
tool is required to
M A
EDA S l TRAv E F
ll operate. ules
R A K E l A
n the B
Air inD nD FOR
A
us ually
hydraulic
solves th system
CE TEST 1/31/18 10:3
1 AM
complete a task, it is
e problem causes most low-
tem, inco
rrec
brake shoe t pushrod length
s, or a dr
s. Low pe
dal als
pedal prob
adjustmen o can be caused by and bleeding
lems, listed in the margin
um brake t, a service a aseic Tool thse syste
64540_ch01_h
r_00 1-04 4.ind d 1
exceed a
When a
sp
gi ven amou
nt of
sh oe
force is
adjuster
th at is
brake that leak inBth
not woan is out of technihy cidr
m
an’saulic sys- next to the procedure.
about 2.5 ecified maximum able to: applied to leak s rkding. Basic adsejut stment, wo
inches (6 be di sta fo th
r e peda tool l rn
fications 4 shou ld nc e. Th d er l, brake pe n shop to we
can ter, you mm) when ter cy linis m
m0aspo aximum da
Fath is chapbe found inInth ect a10 unds (445 etra
anve d l sp Cleal tratve wrlenmchust
Special To
ols
d revim ew of ilu re to exha ■ spe ve tshi
. cle service er fo rN le)akofagfo eed ecifiFlca tionun is no not
are-
pl etion an easurem teenst ust brakdefe ec
bo os r cy lindinformmatine nerc ed is appl
ied . The exac
rmally Brake peda
l effort
co m st em t. Us t pr
e a brake st a m essut re
as te et er io n.
Upon b ra kethsyes e fiv e Tepe an dd
wi ll re su t speci- gauge
safe procedur ■ dal ef mrt
apfo en lt in an in der
■ Perf
orm a pedal :
es air entr gauge to lincorrect pe Tape meas
1. Tuernbra ofke Aeden pairs.
meaas
am suterer cy da
rcdeerapplied l travel or force
ure
drive. ms in rese ssarfy.th
th justgi
ne. On re place cyfolin Service ma
proble as ne cerve vacu ve hi and re the master
ovse wi
to the pe
da
nual
g no se r r’s um Re m cle le ed l with
■ Dia d repai 2. an Inufstaaclltuthre is exha■us
te b en chthb vacun. um
e an m e brake pe dd
an from th tio as sist, .pum
linkag lay to3. Hook e instale labooster.cylinder p the nc
free p the lip dofrag, dal effort befgaorug peeda
pedal .
brake th e tape m e l a th
auon mas ter g seque in l until all
cations the digsta
pin , ncte ea vererhov e brakice b leedin hicle
specifi r stop
e fro
r cymlin-
th ■ Osu ereth hyedto raul peda l ifi
(Fcigve ur
p oo ya rd sti m as e pe da th p sp ec e 4- 3).
gnose al caused b ck on
y l to caeteste foed a
r ge of th
■ Dia need som ede
vehicles■inLoth erct
stru iniog ns
wh een.l rim (F br
e ake pe
ped erform d einof
plac atio ulic dal an
or hard lems and p an
e in tarm
a fo pe ke ighyur dra e 4-4). Yo d measure
p ro b rv ic m ea esu b ra u can use
der id leve i-
l se sh th re.
airs. der flu ed and flu a
rep r cylin lyze the cond ■ Ble
maste .
Terms To Know ■ Che
64540_ch0 ck the cessary. Ana id from its
4_hr_133-
l as
and fil vehi
a
ned
198.ind
cl135e’s b
rake flu
system

er
tion of nce. tomet
List appea
ra
l ABS
Refrac
Specifi
c gravi
ed
ty
ing
To Know Integra ing Surge
b le
Term s l bleed ing
bleed
Terms in this list are Ben ch b leedin
w
g Manua
Non-in
tegral
ABS
ing
Vacuum 1/31/18
10:33 AM
sc re ed
er re ble
also defined in the Bleed
Brake
bleed
ing Pres su
system
ed in g a brake pres-
ble nents of
Glossary at the end of Gravity
O A D TEST aulic compo b the system r and
of
TEM R r hydr e lines can ro de
d othe ter cylin ged or
E SYS der an r or brak the mas
the manual. BRAK
ly, th e m aster cylin aster cylinde which is why linings are correcte d
the m conditions, ds or be
chan

ate safe eaks in g brake pa s must

To oper k properly. L us operatin henever the ny problem
or ro w A ce:
must w cause dange be inspected or braking. rforman
d t p o e pe
sure an system mus plains of or brak use
lic m cause po tires ca
hydrau customer co ca n -i n fl ated
a ons that or over If the
when tely. in g conditi r- in flated, in g power.
immed
ia follo w de ak one
for the ched, un more br pull to
Check or n , mismat cl e re quires may grab or
le m s. W ad ed vehi e br akes
e pr ob lo , th
■ Tir
l brakin
g. heavily to side
ing. A back or side
unequa vehicle load 133
qual front to
■ Une
un eq ual from
load is
side. AM
8 10:33
1/31/1

133
8.indd
r_133-19
ch04_h
64540_

64533_fm_hr_i-xx.indd 12 02/02/18 3:54 pm

 xiii

138 Chapter 4

SERviCE Tip The vehicle’s brake light switch must be activated any time the
brake pedal is moved downward any amount. There is “no free play” allowed with
regard to the brake light switch.

Author’s Notes AuThOR’S nOTE The following procedure is based on a Honda S2000. Other
vehicles have similar procedures. Many vehicles do not have an adjustment for

This feature includes simple pedal height.

explanations, stories, or
Adjusting pedal height
examples of complex topics. 252 One
Cha ptemethod
r6 to adjust the brake pedal height and free play follows. Disconnect and loosen

These are included to help PhOTO SEqUEN

the brake pedal position switch until it is no longer touching the brake pedal lever
(Figure 4-7, A and B). Gain clear access to the floorboard by lifting the carpet and the
insulator
CE(Figure
10 4-8C). Measure the pedal height, (Figure 4-8), from the right center of
students understand difficult Caution
Typical Pro
theced
brake
urepad to the
For vaccleared
uum
floorboard. In the case of this Honda, the pedal height should
be 179 mm or 7 ¹/₆ inches). IfBo oster Tes
necessary to adjust
ting the pedal height, loosen the locknuts, and
concepts. If the switch is not
adjusted correctly, turn the pushrod to obtain the correct measurement (Figure 4-9). With the correct height
obtained, hold the pushrod in place while tightening the locknut to 15 Nm (11 ft. lb.).
the brakes will drag.
This may cause heat Install the brake pedal position switch until its plunger is against the pedal lever and
problems with the
friction materials and
completely pushed into the switch (Figure 4-10). Unscrew the switch until there is
0.3 mm (0.01 inch) between the switch’s threaded end and the mounting pad. Connect
Photo Sequences
poor braking the switch to its electrical harness. Have an assistant check the brake lights as the brake
performance.
pedal is depressed and released. Many procedures are
Adjusting pedal Free play
Using the same Honda vehicle as the example, the pedal free play is checked and adjusted
illustrated in detailed
P10-1 With the engin
gauge to an intake in ethe
below 14 in. Hg of
idling, attach a vacu
manifoldfollowing manner.
port. Any reading
vacuum may indic
um The
P10- engine should be off. Push on the brake by hand while
2 Disconnect the
from the intake mani vacuum hose that runs
Photo Sequences. These
engine problem. ate an fold to the booster P10-3 If you do not
quickly place your
engine stalls. You
should feel strong the
vacuum.
and see if it is colla
feel a
thumb over it befor andPushrod step 2, shut off the engin strong vacuum in
e e, remove the hose
psed, crimped, or ,
photographs show the
Replace it ifLocknut clogged.
needed.
students what to expect
(A)
Brake
switch
Lift floor
mat when they perform particular
(C)
Measuring
procedures. They also
point
familiarize students with a
system or type of equipment
(B)
Pedal (E)
bracket Pedal
height
P10-4 To test the
check valve, shut
operation of the vacu
off the engine and um P10-5 Remove the
that the school might not
check valve from the Standard pedal height
5 minutes. Apply the

there is no power
least one pedal strok
wait for
power assist on at brakes. There should be
e.
Figure If
4-7
booster.

Remove the pedal

(with carpet
179 mm
P10-removed):
6 Test the check
intak(7e mani
in.)
fold end of
valve by blowing into
the
have.
the check valve is
assist on the first
appli catio be a complete block the valve. There should
leaking. position switch
n, or stop lamp Figure 4-8 Remove the floor mat and a portion
age ofof airflow.
switch from the pedal bracket. the carpet to gain clear access to the floorboard.

replace th
e
the wiring parking brake sw Hydrau
harness itch. If th lic Line,
between e
the body lamp is still off,
64540_ch04_hr_133-198.indd 138 1/31/18 10:33 AM
Valve, an
control co find and d Switc
Brake Fl mputer repair th h Service
uid leve an d the sw e op en circui 223
With the l Switch itch. t in
ig Test
to alert th nition on and th
e driver e brake flu
into the of a low-f id level sw
reservoi
for both r body; ot luid condition in itch clos
ed, the br
hers are
Begin by
types. attached the master cylin ake warni
ng lam
to the re de
P10-7 Apply vacu th um to tio en
the boostersu ring that servoir ca r. Some switche p lights
the valve. Vacuume igni th p. Test pr s are built
should be nblock e flu8idChec
end
on and ob of
at th se
P10- le ve
k l
theis at or inciples
not get the state resule switc ed. If you do rve thperfo boos ter air control valve are simila
replace the chec finkdvalvets in h.
step 6 If
and th e la7,mp th of the
step
e w ar
rming
ni a brake
ng lamdrag ne ar th e fu
test. With the
by P10- 9 Turn the front whee r
an.d repa en vehic p. If ll m
whee ls ar k on ls by hand and note
ir the sh go out, d off the floor,
le raise it is , discthe the th
ort circ brake es
amount
To verif pedal to exhareplace th litpump onnect th e reseofrvdrag oir.that is
Turnpresent.
the switc y that the warni ui thet be twter.een th ust resid
boos
e switch
e sw
ual vacu
itc
um from
h. If the e w iri ng connec
h ng
lamp do float or remove lamp will light and the
lamp.
lamp do
es not go tor
es not lig th w
and the ht with th e cap with an hen the fluid leve out,
lamp. If e switch integral l is low, m
ci rc uit contin cl osed, ch sw itc an
As a fin eck for an h and let the flo ually depress
wire betw al check, discon uity is good, re open circ at drop.
ee ne pl ace the sw uit betw If the
If it does n the two term ct the wiring ha itch. een the
not, find inal rness fro switch
64540_ch06_hr_2 compute
252 r.
and repa s in the harness m the sw
itch, and
47-284.indd
ir the op co
en circui nnector. The w connect
a
t betwee ar ju
electric n the sw ning lamp shou mper
itch and ld
al wirin
g Repai the body light.
Wire siz r control 1/31/18 8:57
AM
e is determ
drop allo ined by th
w e amount
or in met ed. Wire size is of cu rrent, th
ric cross- specified e leng
tor. A 20 se in
gauge is ctional area. Th either the Amer th of the circuit,
When much sm e higher ican Wir and the
alle the e voltage
wiring di replacing a wire r than a 12 gaug number in AWG Gauge (AWG)
agrams or , the corr e. the smal syst
ler the co em
prevent
to splice
chafing or in parts books.
aw
damage
to
wires. Ro ire, and use insu the insulation du or wire must be
ect size
Each ha
rness
wire mus
t be used
as show
n on appl
nduc- An America
gauge (A
WG
system for ) is a
n wire Margin Notes
sin flux la tin g tape e to vi br he ld se cure ic ab le specifying
does acid clea atio
The most important terms to know
wire size
-based flu ns the connectio or heat-shrink n. Always use ro ly in place to cross-secti
(conductor
complet x. Apply n during tubing to sin flux
ely ing heat solderin cover all sold on
by a serie al area)
seal unde seal the wiring to shrin g withou splices or er
Many el
rground an
supp
k
electrical d connections. U tubing causes th eroding the mat bare
tility com
t
e tu er ia the
s
numbers; of gauge
the lower are highlighted and defined in the
make th ectrical
system re ly cables. panies us bing to contra l as number,
the wire cro the larger
ese
shorts or repairs in a way pairs require re
gr
with man ounds in the re
that does
no
placing
damaged
ed heat-s
hrink tu and
ct
bing to
ss section
. margin. Common trade jargon also
y pa t in crea w
accessib factors influenci ired area. Severa se the resistanc ires. It is import
requirem
ility of th
ew
ng the ch
oice
l methods
are used
e in the
circuit or an t to
Caution appears in the margins and gives
ents. Th iring, the type of . These factors to lead to Never rep
lace a wi
include th repair damag
1. Wrapp
ing
e three m
ost com conductor and
mon repa siz e type of
ir metho e of wire needed pair required
re
ed wire with one
of
size. Using a smaller
re
some of the common terms used
is damag the damaged insu ds are: rect size the incor-
2. Crimpi
3. Solder
ed an d th la tio nw
ng the co e wiring is unha ith electrical tape
nnections rmed)
, and the
ci rcuit repeated
damage
co uld cause
failure an
d
for components. This feature helps
ing splic (in cases to
When de
ciding w
es with a so
lder-less
connecto
r
where th
e insulatio
n
cle electr the vehi-
ical syste
m. students understand and speak the
connectio here to
ns
of each ot . As a rule, do
her. Use not
cut a da
a wire of have two splices
maged w
ire, avoi
d points
Rosin flu
solder us
x solder
is
language of the trade, especially
Crimping ed
tors . So .
me man
A solder
le ss co
the sam
e size or or connections
la rg er than the w
close to
ith in 1.
other sp
lic es or
trical rep for elec-
airs. when conversing with an experienced
repairs. ufacture nnection uses a wire bein 5 inches (40 mm
Crimping rs re
g solder
com
selfsealin quire the use of pressed junction
se
less conn lf-sealing sold
g replaced
to connec
.
) Heat-shrin
k
plastic tub tubing is
technician.
ections er t two co ing that
is an acce less connections nduc- shrinks in
diameter
ptable w on al l wh en exposed
ay to splic to
64540_
e wire, heat.
ch05_h
r_199-246
.indd 223

1/31/18
8:57 AM

64533_fm_hr_i-xx.indd 13 02/02/18 3:54 pm

 xiv

139
d Service
ake Flui
r and Br
Cylinde
Master

Pedal
Lower lever
l
the peda

(A)
)
(0.01 in.
0.3 mm
knut
hin its loc
switch wit ned. The clear-
0 Turn the tai
Pushrod Figure 4-1 per clearance is ob mm (0.01
Raise 0.3
pedal
until the pros switch should be
the
d turn ance on thi int A.
locknut an or inch) at po
Loosen the longer
Figure 4-9 to make the rod
pu sh rod the mo vement
the
pending on
shorter de (C)
needed.
Locknuts

dal
Brake pe
pad

y
Pedal pla Power Brake Service 271
1–5 mm

Vacuum Check valve

booster
free
the pedal n C
1 Check tur
Figure 4-1 tment is needed, ved.
jus hie
play. If ad per free play is ac n.
until the pro opera tio
rement
stop lamp’s is measu
Check the e is felt. Th to 3/16 inch)
iff resistanc in ch
before a st mm (1 /6 e brake
l travels mm to 5 the locknut on th is cor-
the peda ould be 1
Service Tips measu rin g th e distance l foot pad and sh play by loosen
at the br
ake peda e fre e
adjust th e appropriate di ent is made and
ing
rectio n un til the free
play
recheck
the l free play
Brake peda table on
is not adjus
is taken 11). If necessar y, h in th ju st m
e 4- g the sw
itc the ad itch all vehicles
.
(Figur nut after , check sw
Whenever a shortcut or special Figure 6-26
Honda ispe
The booster
daofl sw
part itch
a VSA
d turnin
on this
an
system.
fo rget
the lock
to tighten htened. th e br
l linkage
ake peda Vacuum
not tig h on .source hose
rect. Do ter the locknut is l stop lamp switc g pedal free play
procedure is appropriate, it is free play
af hanica
has a mec necessar y after
adjustin Figure 6-28 Do not remove the check valve from this
If the car
type of booster. Remove the hose from the check valve
st it if
described in the text. Generally, op er at io n and ad ju
lamp Sw
ch Electrical
it connectors
instead.

300 Serie
s
the Stop Chrysler
these tips describe common Adjusting Figure 6-27 Before removing the booster
fasteners, disconnect g pr
all oc
of the
is based
ureelectrical
edESP
on 2010
win
llothe
The foon
procedures used by experienced R’S nO
AuThO m vehicle.
TEconnectors booster and master cylinder.

its
negative cableanfrom d Mag nubattery. Remove the windshield wiper module
the warping
and justed by usually
adcomponents
technicians. to gain access to the booster.
p lam
could be
p switch p lamp switches
are
nt ac ts
Disconnect the electrical connections at the sto
e, a booster y’s sto the master
and remove s or co
cylinder.
one tim ever, toda switche rms the
Move the master cylinder E Tip At thelin up. H ownot internalthe brake that info dal
SERviCback from ger ed
booster. Do bend re
five diffe
orntdamage
a sensor lines.
Disconnect the vacuum hose
nt to ge
plunthe
t thefrom ithcheck
up four orbut
to valve, dohinot
cle are usingthe check
s remove ) of e brake pe
thvalve
m ou w m e ve CM PP)
from the booster Figure ional units ter systems. So
ct6-28).
(E
Module Pedal Position (B
multifun pu Control e
any com or Engine named the Brak itch.
th at serve m Module (BCM) ns or is
se steering column, in g to th e BPP sw
WARNiNG Before working
Cont rol in or around l. Thethe ps accord ensure that the
air bag system has Body nt of trave Failure
totedischarge. brake lam
had and ex
iontime erate the to properly disarm the air bag
system could result positin serious M will op
e BCinjury.
Switch. Th
10:33 AM
Tape measure 1/31/18
Move inside the passenger compartment, and, if sufficient time has elapsed for the air

Cautions and
bags to disarm, disconnect and remove the stop lamp switch (Figure 6-29). The switch
Ch apter 4 will be replaced with a new one upon installation of the booster. Use a screwdriver to
136 Caution
remove the retaining clip from the booster pushrod, and slide the pushrod from the pedal
pin (refer back to Figure 6-29). Remove the booster’s four mounting nuts, and remove the
booster from the engine
33-198 .ind d 139compartment.
pedal ga
ug
Before even begin-
Brake eff e ning to work on a
ort
hybrid or electric
Warnings
ch04_hr_1
Before
64540_ installing the new booster, ensure that a new booster seal is present on the vehicle, make certain
bulkhead side of the booster (Figure 6-30). Slide the booster into place ap
head and tighten the four mounting nuts to specifications. Position the
Un through
plied
da l
the bulk- that you are aware of Cautions appear throughout
pe
brakebooster pushrod or the procedure to dis-
measure able the high
over the pedal pin and install a new retaining clip. Install and adjust the4-4
switch. Under the hood, install the master cylinder onto the booster
Figure new
a tapelamp
Usestop
dstick reconnect
a yarand
ce
the distan l.
to measure ering wheepower
voltage
supply system
the text to alert the reader
l to the ste all
to potentially hazardous
electrical connections. Install the wiper module and other removed components.
the pe da according to service
from Connect
the battery and road test the vehicle. Brake pedal information.
e ug
effort ga

ke pedal effort
gauge on
the brake
pedal.
materials or unsafe conditions.
SERviCiNG tall the bra
ANInsELECTROhYDRAULiC
Figure 4-3
POWER BOOSTER SYSTEM Warnings advise the student
Hybrid vehicles, as well as some conventional gasoline vehicles, use an electric brake
booster pump (often referred to as a hydraulic power unit Figure 6-31) used to pressurize
of things that can go wrong if
brake fluid for use in a hydraulic booster system, which has the master cylinder
instructions are not followed
or if an incorrect part or tool is
used.
References to the
64540_ch06_hr_247-284.indd 271
1/31/18 8:57 AM

Classroom Manual Apply the

specified
amount of
pedal force.

the brak
e pedal
Figure 4-5
force re gisters on
ified test
References to the appropriate e pedal un
til the sp
ec
the brak .
4. Apply uge (Figure 4-5) s-
page in the Classroom Manual effort ga
fer to the
vehicle’s
service hi
for exam
-
nosis, re ir order,
any diag ning to this repa quick, accurate
appear whenever necessary. E Ti p Be fore st ar tin
cent hi
g
st or y pe rtai
ay point
th e w ay to a
SERviC ote any re repair m
Although the chapters of the tory if av
ailable. N A recent brake
e pedal lo
w.
d
ple, brak e increase
two manuals are synchronized, diagnosis
.
e
sure or ya
rdstick. Th cle service
hi
tape mea n listed in the ve rod adjust-
n on th tio sh
l positio
material covered in other the chan
ge in peda the maximum aulic system and
t exceed the hydr
specifica check pu e also can
rking brak
5. Note should no ok for a leak in justed pa
poorly ad
chapters of the Classroom distance
man ua l. If it does , lo
s, ba d sh oe adjust er s, or a

orn shoe l travel.

ment. W
Manual may be fundamental to cause ex
cessive pe
da
EnT
DJuSTM
AnD A d the
the topic discussed in the Shop p lAY in S p ECTiOn
ake pe da l or bo oster pu
shrod an at
so th
must exist pedal
F R E E the br e pl ay
pEDAl
n
e betwee ific amount of fre ased and so that
Manual. ay is the
clearanc
r. A spec dal is rele
dal free pl e master cylinde ied when the pe
Brake pe on in th ia lly appl
pi st rt
Manual primar y y piston is not pa
Classroom ar
the prim 10:33 AM
page 75 1/31/18

d 136
33-198.ind
ch04_hr_1
64540_

64533_fm_hr_i-xx.indd 14 02/02/18 3:54 pm

 xv

140 Chapter 4

Stoplamp
switch

Stoplamp
switch mou
nting
bracket

Brake pedal
Figure 4-12 lever
Pull
before installa the switch plunger all the
tion way out
and not release . The pedal should be lock
d until the swit ed
ch is installed. down
Use a brake
pedal
for a depressor depressor to hold the
). Rotate the brake pedal
and pull rea stop lamp sw down (check
rward on the itch approxim the alig
ately 30 degree nment machine
hand force
should be hea
rd as the plu
sw
only, pull the itch. It should separate
switch plung
er out to its
from its mo
ful
s counterclock
unt (Figure wise
4-12). Using
Customer Care
Ensure the bra ng er ratchets out. ly ext ended positi
ke ped on. Low clic
switch’s index
switch about
key to the no
30 deg
al is down as
far as it will
tch in the bra
cket and pu
go and is firm
ly held in pla
ks
This feature highlights those little things
Apply foot for rees clockwise until it loc sh the switc ce. Align the
to gently ris ce to the brake
e until it sto pedal and rem
ks. h int o pla ce. Rotate the a technician can do or say to enhance
stops movin ps. Using gen ove the pedal
adjustment
g. This will
is initially che
ratchet the
tle hand for
switch plung
ce, pull up on
er to the cor
depressor. All
the brake ped
ow the pedal customer relations.
pedal is dep cke al until it
ressed and rel d by having an assistant rect position
. The switch
where the cru eased. Howe obser ve the
ise ver, the final brake lights
at a safe speed. control can be safely use check requir
es
as the brake
Once the sys d. During the roa a road test on
should turn tem is stabilize d test, engage a roa
off. If not, the
n the switch d, depress the the cruise con d
Caution must be che brake slightl trol
cked and rea y. The cruise
Do not release
the djusted as nee control
brake pedal by ded.
pul CuSTOMER
ing the depress l- CARE A cus
or
and letting the out his or her car tomer’s only
is contact, lite
slam up to its
pedal mance by “pe through the brake pedal. rally, with the
brake
dal feel.” It is Customers ten
The stop lamp p.
sto brake pedal
before startin
always a goo
d idea to eva d to judge bra system in
switch g any brake luate the fee ke perfor-
will not adjust pedal feel sho job. Then wh l and action
prop- uld be notic en you delive of the
erly and may brake pedal eably impro r the
be action is air ved
damaged. lot to ensure in the system . The biggest cause of spo finished job,
customer con , so careful ble ngy or low
fidence. eding of the
system will do
a

Brake peda
l positionSwitch
Many late-m
odel vehicle
the brake ped s use a BPP sen
al sor to inform
supplies a 5-v position (Figure 4-13). the body con
trol module
olt reference Th
signal and gro e BPP sensor is a poten (BCM) of
und to the sen tiometer. Th
sor and the e BC
sensor suppli M
es an
Name ______
64540_ch04_h
r_133-198.ind ____________
d 140 ____________ Drum Brake
________ Service
425
DIAGNOSIN Date ______
G DRUm BR ___________
Upon comple AkE PROB
tio
ing, grabbing, n of this job sheet, you
LEmS JO
1/31B
/18 Sh

ASE Educa
dragging or
tion Founda
pedal pulsat
tion Correlat
will be able
to
ion problems diagnose poor stopping,
. noise, pull- 36
10:33 EE
AM T
Job Sheets
This job she ion
et addresses
C.4.
Inspect wheel
the following
MLR task: Located at the end of each chapter, the
needed. (P-2) cylinders for leaks and
This job she
et addresses
the following
proper operat
ion; remove
and replace
as
Job Sheets provide a format for students
C.1. AST/MAST
Diagnose po
or
pulsation con stopping, noise, vibrat
cerns; determ
tasks:
ion, pulling,
to perform procedures covered in the
C.5. ine necessary grabbi
Inspect wheel
and replace cylinders for leaks and
as needed. (P-
action. (P-1) ng, dragging or pedal
proper operat
chapter. A reference to the ASE Education
2) ion; remove
Tools and Ma
terials
Foundation task addressed by the
• Basic hand
Protective
tools
Clo
procedure is included on the Job Sheet.
Goggles or saf thing
ety glasses wit
Describe the h side shield
s
vehicle being
Year ______ worked on:
________ Ma
ke _________
Engine type _____ Model
and size ___ ____________
____________ __ VIN ______
Procedure ____________ ________
____________
____________
1. Begin the _________
inspec
unusual wear tion of the drum brake
or improper sys
inflation. Wh tem by checking the tire
at did you fin s for excessive
d? or

2. Wheels for
bent or warped rim
s. What did
you find?

3. Wheel bea
rin gs for loosen
ess or wear.
What did you
find?

4. Suspensio
n system for wo
rn or broken
components.
Wh at did you fin
d?
5. Brake flu
id lev el in the ma
ster cylinder.
What did you
find?

6. Signs of
leakag
at each wheel e at the master cylinder,
. What did you in brake line
find? s or hoses, at
all con nections, and

64540_ch08_h
r_373-434.ind
d 425

02/02/18 1:15
pm

64533_fm_hr_i-xx.indd 15 02/02/18 3:54 pm

 xvi

424 Chapter 8
S can be used
LENG E qUESTION n A says a tire
depth gauge
B says
ASE ChAL a lath e, 4. Technicia
re lini ng thickness
. Technician
lining thick-
m on to me asu um
cus sin g mo unting a dru unt s to ma ker s spe cify a minim ) above the
1. While dis ece drum mo most car or 0.75 mm
Ase Challenge Questions Technician A
the lath e arb
says a two-pi
or with tapere
d or spherical
ece dru m is cen
cones.
ter ed
ness of 1/32
sho e tab le or
inch (0.030 in. t rivet head. Who is
above the clo
ses
says a one-pi d cone and
Technician B spring-loade correct? C. Both A and
B
arbor with a
Each technical chapter ends with five ASE on the lathe
clamp ed in pla ce by two large
cup-shaped
adapt-
A. A only D. Neither A
nor B
onl y
rec t? B. B . Tec ician
challenge questions. These are not mere review ers. Who is
A. A only
cor
C. Both A and
B
nor B 5. Wheel cyl
inders are bei
ng discussed
inder may4cau
hn
se
D. Neither A t a lea king wheel cyl say99s that
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questions; rather, they test the students’ ability to B. B only
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tivating
Case Studies
to
ABS ac ng appeared g to a slow
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ai ev d d
U D y r compl inspected, vement an tool an of
ST e ow ne ere pa e sc an
CaSe with th akes w on dr y
e shop ere made, br the vehicle e technician had to be th oblem.
read th e source
Each chapter ends with a Case Study e came
in to th
checks
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e BPM
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describing a particular vehicle problem and speed. r the fact th ok an assist cian finally
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ator, th lp. The forem t appear to replaced
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stop. Th ng looked no acing the ex shop forem en though
the logical steps a technician might use to pl e
ever ythi lem. After re d to go to th the drums, placement. There are tw hen you need
de ce
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o lesson
w
help.
the prob int he deci and resurfa t of needing ed normally. technician
solve the problem. These studies focus on At th is po
the rear
sh oe s
worn to
replace any way or achined, the to ask a m
th e po in
vehicle
pe rfo rm
ore expe
rie nc ed
cus-
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nated drums were
m
be afra
id with a k
system diagnosis skills and help students gain th
e
and th basics, and
e
do not
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4ro2b3lem
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Saebrvraic it is import ician B say-
as
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ra
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y l e RevIe is cu ssed. ex ac tly t to as t? B 1/31/18 10:16

AM
T eing d -7 mu
st port an correc A an d
aSe-S BS is b elphi DBC in sit is im ice. Wbhraokeis lathe, i-C. Both B
g an A D rv on a x A nor
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Ase-Style Review Questions T e re ru rg e er . rr ts to an A w ct ?
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1/31/1
8 9:03 AM

and re ian B doesC. und inolt ag rr ec t? ther A

D. Nei
review the chapter as well as to prepare for T ec h n ic
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o
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gag th n A sa wheel cylin ician B says re
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only heel 9. Tec wear at th ition. Tech
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the to more wear cond er vo brake installed in
B. B o
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4. D li
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areas than th ho is corr C. Bo A nor
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ys th at B o th . A o nly n re tu rn
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A. A
m d is c ard hich T ec h nician use brake at the same or an inop
nly e dru e ter to w 10 . can ca ys th king plate
B. B o ys th at th
diam ic ian B ri n gs n B sa
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n
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not C. Bo or B
n and e er A n
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the dru the drum we ar dim ter. Who is only
D .
th at w ab le m e A . A
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A. A
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B. B o

:16 AM
8 10
1/31/1

3
d 42
434.ind
r_373-
ch08_h
64540_

64533_fm_hr_i-xx.indd 16 02/02/18 3:54 pm

 xvii

Disc Brake Service 355

Name ___________________________________
___ Date _________________
JOB ShEE T Job Sheets
DIAGNOSING DISC BRAkE PROBLEMS
30 Located at the end of each chapter, the
be able to diagnose poor stopping, noise,
Upon completion of this job sheet, you will
pulling, grabbing, dragging, or pedal pulsatio
n problems. Job Sheets provide a format for students to
ASE Education Foundation Correlation perform procedures covered in the chapter.
AST task:
This job sheet addresses the following AST/M
Diagnose poor stopping, noise, vibration,
pulling, grabbing, dragging, A reference to the ASE Education Foundation
D.1. y action. (P-1)
or pulsation concerns; determine necessar task addressed by the procedure is included
Tools and Materials on the Job Sheet.
Basic hand tools
Protective Clothing
Goggles or safety glasses with side shields
Describe the vehicle being worked on:
_
Model ______________ VIN ______________
Year _______________ Make ______________
Engine type and size _______________
Procedure
e or
system by checking the tires for excessiv
1. Begin the inspection of the disc brake
did you find?
unusual wear or improper inflation. What ___
___________________________________
___________________________________
did you find?
2. Wheels for bent or warped wheels. What ___
___________________________________
___________________________________
ss or wear. What did you find?
3. Wheel bearings for loosene ___
___________________________________
___________________________________
components. What did you find?
4. Suspension system for worn or broken ___
___________________________________
___________________________________
. What did you find?
5. Brake fluid level in the master cylinder ___
___________________________________
___________________________________
hoses, at all connect ions, and
, in brake lines or
6. Signs of leakage at the master cylinder
at each wheel. What did you Ap pe nd ix
find?
___
___________________________________
Ase Practice Examination
______________ _______ _______ _______
As e pr Ac tic e ex
7. Road test the vehicle. As you apply the
brake pedal, check forAm in At io n
excessiv e travel and

sponginess. What did you find?

______________ _______ _______ _______ _______ _______________________________ A 50-question ASE practice exam, located in
1. Technicia
8. Listen n A says
for noises, justifthe
notthat obvious sounds of grinding pads or pad linings,
the master cylin
but the Appendix, is included to test students on
pushrod icalisclanks, clunks, and rattles. Whatder did you find? 6. A vehi
mechan
not be able
_______
adjusted
to fully
_______
too long, the brakes migh
appl_______
_______ ______________t ______________
y. Technicia
cle drift
Tech_______
s to the
_______ ___right while driving.
nician A says that a crim
the content of the complete Shop Manual.
the master cylinder push n B says that if ped line to the left
rod applied, whefor
check el coul
a bad
d caliper
be the caus
vehicle pulls to one side when is adjuthe brakes
sted are
too short, e. Technician B says that
9. If the
thebrak es migh
caliper
t drag
at one . Who Also
wheel. is check
corr ect? for signs of grease orthe inter
brake fluid that
ior of themay
righ t brak e hose could be dam-
or loose d brake pads.
A. A only
have contaminated the pads and rotor. Check for distorted oraged
C. Both
damage. Who is corr ect?
A and B
B. B only A. A only
D. Neither A nor B C. Both A and B
2. While discussing mas B. B only
ter cylinders, Technicia D. Neither A nor B
says normal brake linin nA 7. Technician A says serv
g wear causes a slight ice information circuit
in fluid level. Technicia drop grams or schematics mak dia-
n B says a sure sign of e it easy to identify com
brake fluid contamination mon circuit problems -
with mineral oil is the . Technician B says if seve
swelling of the master circu its fail at the same time ral
02/02/18 12:45 pm
cylinder cover diaphrag , check for a common
Who
64540_ch07_hr_285-372.indd 355 is correct? m. power or ground conn
ection. Who is correct?
A. A only A. A only
C. Both A and B C. Both A and B
B. B only B. B only
D. Neither A nor B D. Neither A nor B
3. Technician A says that 8. Tech nician A says that ther
master cylinder leaks e is a vacuum check
be internal or external can valve in line between man
. Technician B says that ifold vacuum source
leaking master cylinder a and the booster. Technicia
will remove paint from n B says this check
the area below the mas valve is to allow air pres
ter cylinder. Who is sure into the booster dur-
correct? ing wide-open throttle
operation of the engine.
A. A only Who is correct?
C. Both A and B
B. B only A. A only
D. Neither A nor B C. Both A and B
4. While discussing brak B. B only
e lines, Technician A says D. Neither A nor B
that copper tubing can 9. Dru m brak es are being discussed. Tech
be used for brake lines
Technician B says that . says that a grabbing brak nician A
brake lines can use doub e could be traced to a
flare or an ISO flare fittin le- leaking axle seal. Tech
gs. Who is correct? nician B says that a leak
A. A only wheel cylinder can also ing
C. Both A and B cause drum brake grab
bing. Who is correct? -
B. B only
D. Neither A nor B A. A only
5. Technician A says to C. Both A and B
replace a double-flare B. B only
with an ISO-type fittin fitting D. Neither A nor B
g as new brake lines are
required. Technician B 10. Befo re tryin g to remove a brake drum
says that flexible brake
hoses allow movement Technician A uses the for service,
of components. Who self-adjuster to back off
correct? is brake shoes. Technicia the
n B adjusts the parking
A. A only brake cable to remove
C. Both A and B the slack . Who is corr
A. A only ect?
B. B only
D. Neither A nor B C. Both A and B
B. B only
D. Neither A nor B

539

64540_em_app_hr_5
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1/31/18 3:28 PM

64533_fm_hr_i-xx.indd 17 02/02/18 3:54 pm

 xviii

SUPPLEMENTS
Instructor Resources
The Today’s Technician series offers a robust set of instructor resources, available online
at Cengage’s Instructor Resource Center and on DVD. The following tools have been
provided to meet any instructor’s classroom preparation needs:
■■ An Instructor’s Guide provides lecture outlines, teaching tips, and complete answers
to end-of-chapter questions.
■■ Power Point presentations include images, videos, and animations that coincide with
each chapter’s content coverage.
■■ Cengage Learning Testing Powered by Cognero® delivers hundreds of test questions
in a flexible, online system. You can choose to author, edit, and manage test bank
content from multiple Cengage Learning solutions and deliver tests from your LMS,
or you can simply download editable Word documents from the DVD or Instructor
Resource Center.
■■ An Image Gallery includes photos and illustrations from the text.
■■ The Job Sheets from the Shop Manual are provided in Word format.
■■ End-of-Chapter Review Questions are also provided in Word format, with a separate
set of text rejoinders available for instructors’ reference.
■■ To complete this powerful suite of planning tools, a pair of correlation guides map
this edition’s content to the NATEF tasks and to the previous edition.
MindTap for Today’s Technician: Automotive Brake Systems, 7e
MindTap is a personalized teaching experience with relevant assignments that guide stu-
dents to analyze, apply, and improve thinking, allowing you to measure skills and out-
comes with ease.
■■ Personalized Teaching: Becomes yours with a Learning Path that is built with key stu-
dent objectives. Control what students see and when they see it. Use it as-is or match
to your syllabus exactly—hide, rearrange, add, and create your own content.
■■ Guide Students: A unique learning path of relevant readings, multimedia, and activi-
ties that move students up the learning taxonomy from basic knowledge and compre-
hension to analysis and application.
■■ Promote Better Outcomes: Empower instructors and motivate students with analyt-
ics and reports that provide a snapshot of class progress, time in course, engagement
and completion rates.

64533_fm_hr_i-xx.indd 18 02/02/18 3:54 pm

 xix

REVIEWERS
The author and publisher would like to extend special thanks to the following instructors
for reviewing the draft manuscript:

Rodney Batch Larry Stanley

University of Northwestern Ohio Arizona Western College
Lima, OH Yuma, AZ

Christopher J. Marker Claude F. Townsend

University of Northwestern Ohio Oakland Community College
Lima, OH Bloomfield Hills, MI

Tim Pifer
Midlands Technical College
Columbia, SC

64533_fm_hr_i-xx.indd 19 02/02/18 3:54 pm

64533_fm_hr_i-xx.indd 20 02/02/18 3:54 pm
 Chapter 1
Brake System Fundamentals

Upon completion and review of this chapter, you should be able to:
■■ List and describe the operation of the ■■ Describe the use of valves and lines
basic parts of a brake system. to direct and control the hydraulic
■■ Describe the operation of the brake fluid.
system during and after pedal ■■ Discuss the purpose of brake power
application. boosters and the parking brake.
■■ Discuss the increasing use of disc ■■ Discuss the general operation of elec-
brakes instead of drum brakes. tronic and active braking systems.
■■ Describe a typical brake hydraulic ■■ Discuss the general operation of trailer
system. brakes and air brakes.

Terms To Know
Active braking Friction Service brakes
Actuators Fulcrum Steering wheel position
Air brakes Lateral acccelerometer sensor
Antilock brake system (ABS) Leverage Stroke sensor
Automatic ride control Lockup Stroke simulator
(ARC) Master cylinder Traction-control system (TCS)
Bulkhead Negative wheel slip Vehicle stability control
Caliper Parking brakes (VSC)
Disc brake Positive wheel spin Wheel cylinder
Drum brake Pressure Wheel speed sensors
Force Regenerative braking Yaw

INTRODUCTION
The brake system is one of the most important systems on a vehicle. It has four basic
functions:
1. It must slow a moving vehicle.
2. It must bring a vehicle to a stop.
3. It must hold a vehicle stationary when stopped.
4. It allows directional control during maximum braking.
If the brake system does not operate properly, the driver and passengers could be
injured or killed in an accident. Technicians who service the brake system must be highly
skilled experts because the work they do can save lives. In this chapter, we start our study
of the brake system by presenting the basic concepts and parts of all brake systems.

64533_ch01_hr_001-019.indd 1 02/02/18 6:06 pm

 2 Chapter 1

Anti-lock brake system

This chapter also highlights some of the dynamics associated with braking and con-
(ABS) is a braking trolling a vehicle. If all the various dynamics are not considered during the design stage,
system that is designed most braking systems will under brake or over brake. When the brake system is not
to prevent the brakes designed or operating correctly, it will be up to the driver to compensate, usually with
from locking up on hard
stops so that the driver poor results. In many cases, the human response is either too slow or too quick to react
can maintain control of to a braking situation. In both cases, a loss of vehicle control is probably unavoidable. To
the vehicle. prevent this, antilock brake system (ABS) and stability control have been added to help
the driver maintain control.

Service brakes: The

brakes that are used to
BRAKE SYSTEM OVERVIEW
stop the vehicle.
The complete brake system consists of the major components shown in Figure 1-1. These
are the service brakes, which slow and stop the moving vehicle, and the parking brakes,
Parking brakes: The which hold the vehicle stationary. On late-model vehicles, the ABS is a third major sub-
braking system that is
used to hold the vehicle
system; and new cars now also include traction control and stability control as part of the
stationary while parked. brake system functions. Hybrid and electric vehicles make use of regenerative braking,
which captures some of the energy normally lost as heat on the pads and rotors while
stopping. Regenerative braking systems use electrical generators to help slow the vehicle
Regenerative braking
recapture some of the
during gradual stops and help recharge the electric batteries. Electric and hybrid vehicles
lost energy during still have conventional hydraulic brakes to stop the vehicle quickly when necessary.
­braking on hybrid Regenerative brakes are a blending of the generators’ ability to help slow the vehicle and
vehicles. conserve energy and the hydraulic systems’ ability to stop the vehicle quickly.

Leverage and the Brake Pedal Design

Author’s Note A fulcrum is the point at which one lever pivots or sits to
apply force to another lever or device. A seesaw pivots on a fulcrum.

Hydraulic power
brake booster
Rear disc or drum
Master cylinder brakes
and ABS
hydraulic unit

ABS wiring
harness

ABS
computer

Parking
brake lever
Brake
pedal

Front disc brakes

Figure 1-1 A typical automotive brake system comprises these major components and subsystems.

64533_ch01_hr_001-019.indd 2 1/31/18 10:39 AM

 Brake System Fundamentals 3

Brake pedal
pivot (fulcrum)

2 inches
250
pounds
of force

10 inches
Master
cylinder

Lever
50
pounds Bulkhead
of force

Brake
pedal

Figure 1-2 The brake pedal assembly uses leverage to increase force applied to the
master cylinder.

Braking action on an automobile begins with the driver’s foot on the brake pedal. The
driver applies force to the pedal (which we learn more about later), and the pedal transfers
that force to the master cylinder pistons. The brake pedal also multiplies the force of the
driver’s foot through leverage.
The brake pedal is mounted on a lever with a pivot near the top of the lever. The
movement of the pedal causes a pushrod to move against a master cylinder. The master
cylinder is mounted inside the engine compartment on the rear bulkhead. The master The bulkhead separates
the engine compartment
cylinder is a hydraulic pump that is operated by the driver through the brake pedal. from the passenger
Most brake pedal installations are an example of what is called a second-class lever. compartment.
In the science of physics, a second-class lever has a pivot point (or fulcrum) at one end
and force applied to the other end. A second-class lever transfers the output force in the
The fulcrum is the
same direction as the input force, and multiplies the input force, depending on where the support for a lever to
output load is placed. The brake pedal installation shown in Figure 1-2 has a 10-inch pivot on.
lever, and the load (the master cylinder pushrod) is 2 inches from the fulcrum (8 inches
from the pedal). The pedal ratio, or the force multiplying factor, is the length of the lever
divided by the distance of the load from the fulcrum. In this case, it is:

10
5 5 :1
2

If the driver applies 50 pounds of force to the pedal, the lever increases the force to
250 pounds at the master cylinder. When the driver applies 50 pounds of input force, the
pedal may travel about 2.5 inches. When the lever applies 250 pounds of output force, the
pushrod moves only 0.5 inch. Thus, as leverage in a second-class lever increases force, it Leverage is the use of a
reduces distance by the same factor: lever and fulcrum to
create a mechanical
advantage, usually to
2.5 inches increase force applied
5 0.5 inch to an object.
5

Service Brake History and Design

Modern automobile brakes evolved from the relatively crude brakes of horse-drawn vehi-
cles. The earliest motor vehicle brakes were pads or blocks applied by levers and linkage

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 4 Chapter 1

to the outside of a solid tire on a wooden-spoked wheel. The same principles of leverage
that work in modern brake pedal installations increased the force of the brake pad applied
to the solid tire. These brakes worked well with speeds of 10 mph to 20 mph and little
traffic. Higher performance (30 mph and beyond) and pneumatic tires meant that early
wagon brakes were short-lived on automobiles.
By the end of the first decade of the twentieth century, automobiles were using either
external-contracting band brakes or internal-expanding drum brakes. A few internal-
expanding band brakes were tried on some early motor vehicles. External-contracting brakes
Friction is the force that have a band lined with friction material wrapped around a drum located on the driveline
resists motion between or on the wheels. The band is anchored at one end or at the center; levers and linkage tighten
the surfaces of two
objects or forms of matter. the band around the drum for braking force. The service brakes on Ford’s famous Model T
were a single contracting band applied to a drum inside the transmission.
Band brakes, either internal or external, lose their effectiveness when higher braking
A drum brake is a brake force is needed. When you study drum brakes, you will learn about the mechanical servo
in which friction is action of brake shoes. It is very difficult to develop servo action with an internal band
generated by brake
shoes rubbing against brake, and higher brake force is thus needed. Servo action on an external band brake tends
the inside surface of a to make the brake grab at high brake forces and high drum speed. Other problems associ-
brake drum attached to ated with band brakes include dirt and water damage and loss of friction with external
the wheel.
bands and the tendency of these brakes to lock if the drum overheated and expanded too
much. Internal band brakes also suffer from band and drum overheating and reduced
braking force.
As drum brakes evolved, internal-expanding shoe-and-drum brakes became the stan-
dard. External-contracting band brakes were used as parking brakes until the late 1950s,
but their days as service brakes were over by the late 1920s.

Drum Brakes. By the mid-1920s, drum brakes with internal-expanding shoes were the
general rule. Early drum brakes were operated mechanically by levers and linkage
(Figure 1-3). Expensive luxury cars such as the 1921 Duesenberg Model A were among
the first to have hydraulic drum brakes. Hydraulic brakes started to appear on lower-
priced cars in the mid-1920s with Chrysler’s Light Six, which became the Plymouth. Ford
Motor Company, however, used mechanical brakes through the 1938 model year.

Author’s Note There were two major reasons for the increased use of
hydraulically applied brakes over the mechanically-applied ones: (1) The four
brakes never seemed to apply the same amount of braking force at the same time
because (2) the brake linkages required almost constant re-adjustment to make the
brake work at all. The only reason mechanical brakes were ever practical was the
fact that roads were rough and couldn't be traveled at high speeds.

The rigid brake shoes used with drum brakes could be made stronger than the flexible
bands of earlier brake designs. This eliminated breakage problems that occurred with greater
braking forces that were required as automobiles got more powerful and faster. With hydrau-
lic actuation, four-wheel drum brakes remained the standard braking system for most cars
into the middle and late 1960s. With the coming of Federal Motor Vehicle Safety Standards
(FMVSS) 105 in 1967, brake systems had to pass specific performance tests that made front
disc brakes the general rule in the 1970s. Even at the beginning of the twenty-first century,
Disc Brakes: A braking however, drum brakes are still used on the rear wheels of many cars and light trucks.
system that forces two
brake pads on opposite Disc Brakes. Modern automotive disc brakes were developed from aircraft brakes of
sides of a spinning rotor World War II. Known originally as “spot” brakes, disc brakes work by applying pressure
to stop the vehicle
to two brake pads on opposite sides of a spinning rotor attached to the wheel hub

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 Brake System Fundamentals 5

Brake pedal Brake pedal rod

Brake pedal
pivot

Cam

Brake shoes

Drum
Figure 1-3 A simple mechanical expanding drum brake.

(Figure 1-4). Disc brake pads are mounted in a caliper that sits above the spinning rotor. A caliper is a major
The caliper is either fixed or movable on its mounting. With a fixed caliper, hydraulic component of a disc
pressure is applied to pistons on both sides to force the pads against the rotor (Figure 1-5). brake system that
houses the piston(s)
With a movable caliper, pressure is applied to a piston on the inboard side only. This forces and supports the brake
the inboard pad against the rotor, and the reaction force moves the outboard side of the pads.
caliper inward so that both pads grip the rotor (Figure 1-6).
All the friction components of a disc brake are exposed to the airstream, which helps
to cool the brake parts and maintain braking effectiveness during repeated hard stops from
high speeds. This, in turn, leads to longer pad life and faster recovery from brake fade.
Disc brakes do not develop the mechanical servo action that you will learn about as you
study drum brakes. Therefore, disc brakes require higher hydraulic pressure and greater
force to achieve the same stopping power as a comparable drum brake. These pressure
and force requirements for disc brakes are met easily, however, with large caliper pistons

Caliper
Boot

Seal

Caliper
Hydraulic Hydraulic
Hydraulic pressure pressure
pressure

Piston

Piston

Hydraulic
pressure
Rotor

Figure 1-4 Hydraulic pressure in the caliper

forces the disc brake pads against the spin- Figure 1-5 Hydraulic pressure is applied equally to pistons on both sides
ning motor. of a fixed caliper.

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 6 Chapter 1

Reaction
Caliper

Action
Piston

Hydraulic
pressure

Figure 1-6 Hydraulic pressure in a movable

caliper forces the piston in one direction and
the caliper body in the other. The resulting
action and reaction force the pads against
the rotor.

A BIT OF HISTORY
Hydraulic brakes were invented in 1918 in the California shop of Malcolm Loughead. He later
changed the spelling of his name to Lockheed, and he and his brother founded the aircraft c­ ompany
of that name. The Lockheed hydraulic brake first appeared on the 1921 Duesenberg Model A.

and power brake boosters. Because their advantages far outweigh any disadvantage, disc
brakes have become the universal choice as the front brakes on all cars and light trucks
built since the 1970s. Additionally, four-wheel disc brakes became standard equipment
on high-performance automobiles, SUVs, and some trucks.

Brake Hydraulic Systems

Although brake systems have been changing recently, hydraulic operation of service
The master cylinder is
the liquid-filled cylinder brakes has been the universal design for more than 70 years. The complete hydraulic
in the hydraulic brake system consists of the master cylinder, steel lines, rubber hoses, various pressure-control
system in which valves, and brake apply devices at each wheel.
hydraulic pressure is
developed when the Master Cylinder. The master cylinder is the start of the brake hydraulic system. It actu-
driver depresses a foot ally is a cylindrical pump. The cylinder is sealed at one end, and the movable pushrod
pedal.
extends from the other end (Figure 1-7). The pushrod moves a pair of in-line pistons that

Secondary output port Primary output port

Secondary Primary
reservoir reservoir

Pushrod

Piston
return
spring
Seal
Spring
Seal
Seal Seal
Seal
Figure 1-7 The master cylinder is a cylindrical pump with two pistons that develop
pressure in the hydraulic lines to the front and rear brakes.

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 Brake System Fundamentals 7

Right front Right rear

Master
cylinder

Secondary
piston

Primary
piston

Left front Left rear

Figure 1-8 Each master cylinder piston feeds one system of a split hydraulic
brake system. Shown is a diagonally split system.

produce the pumping action. When the brake pedal lever moves the pushrod, it moves
the pistons to draw fluid from a reservoir on top of the master cylinder. Piston action then
forces the fluid under pressure through outlet ports to the brake lines. Pressure is the force
All master cylinders for vehicles built since 1967 have two pistons and pumping cham- exerted on a given unit
of surface area—force
bers, as shown in Figure 1-7. Motor vehicle safety standards require this dual-brake divided by area—
system to provide hydraulic system operation in case one hose, line, or wheel brake assem- measured in pounds per
bly loses fluid. Because the brake hydraulic system is sealed, all the lines and cylinders are square inch (psi) or
kilopascals (kPa).
full of fluid at all times. When the master cylinder develops system pressure, the amount
of fluid moved is only a few ounces.
Split Systems. Modern-day vehicles have split brake systems. The pre-1970s vehicle had
a single hydraulic system serving all four wheels. A leak anywhere in the system resulted
in a complete braking failure. The split system was designed to prevent a total system fail-
ure. This required the use of a dual-piston master cylinder and the inclusion of various
valves. A split system is fed by one piston in the master cylinder and feeds two wheel brakes
of the vehicle. There are two types of split systems: diagonal and front/rear. The diagonal
has one system feeding a front-wheel brake and the rear, opposing-side-wheel brake, that
is, left front and right rear (Figure 1-8). The second diagonal split is to the other wheel
brakes. The front/rear split is exactly as it sounds. One side or split feeds the rear-wheel
brakes, and the other feeds the front wheels (Figure 1-9). Both types of split have advan-
tages and disadvantages, but each prevents complete system failure from a single leak.

Hybrid Master Cylinders

Hybrid vehicles braking systems have some significant differences as compared to most
conventional automobiles. One reason for this is regenerative braking used during light
to moderate braking. Regenerative braking can slow the vehicle and recover much of the
energy used by using the drive motor as a generator. Another reason is that the engine
Stroke sensor informs
may not be running to provide vacuum to the conventional brake booster. These two fac- the brake controller how
tors produce a master cylinder used somewhat conventionally to produce pressure, but fast and how much
this pressure is amplified by the brake actuator (Figure 1-10) to apply the appropriate pressure the driver
applied to the brakes.
pressure to the wheel calipers. The brake stroke sensor ( Figure 1-11) informs the brake

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 8 Chapter 1

Right front Right rear

Master
cylinder

Secondary
piston

Primary
piston

Left front Left rear

Figure 1-9 A front/rear split dual hydraulic brake system.

Stroke sensor

Figure 1-10 A hybrid brake actuator for a Toyota Figure 1-11 A brake pedal stroke sensor tells the braking
Camry contains a pump to boost brake pressure system how far and how fast the brake pedal is being
instead of using a vacuum booster. depressed.

controller how fast and how much pressure the driver applied to the brakes; the brake
controller then decides on what ratio of regenerative braking to hydraulic braking needs
to be applied. If the braking is light, then the controller may decide to use only the regen-
erative braking system to stop the vehicle. If the stop is moderate, the controller may
command regenerative and hydraulic braking. If the stop is panic in nature, then the
hydraulic braking system will be the dominant choice. In these systems, the stroke
­simulator (Figure 1-12) provides appropriate brake pedal feedback to the driver; in other
Stroke simulator words, the brakes should feel normal to the driver.
provides brake pedal Brake Lines and Hoses. The rigid lines or pipes of a brake hydraulic system are
feedback to the driver.
made of double-walled steel tubing for system safety. Flexible rubber hoses connect

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 Brake System Fundamentals 9

Front right

Front left
Rear right

Rear left

Pressure
sensors
Isolation
valves
Pressure

Pressure

Pressure
sensor 2

sensor 1

sensor 3
simulator
Stroke
cylinder
Master

Accumulator
Pump
Reservoir
Fluid

Figure 1-12 Hybrid ABS system showing stroke simulator that gives a normal pedal feel to the driver.

the wheel brakes to the rigid lines on the vehicle body or frame (Figure 1-13). The
front brakes have a rubber hose at each wheel to allow for steering movement. Rear
brakes may have separate hoses at each wheel or a single hose connected to a line on
the body or frame if the vehicle has a rigid rear axle. Brake lines and hoses contain the
high-pressure fluid, and the fluid acts as a solid rod to transmit force to the wheel
cylinders and caliper pistons.

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 10 Chapter 1

Mounting Caliper
Slot for mounting clip connection

Connection between Flexible hose

steel and flexible hose

Figure 1-13 A flexible hose provides a connection between the vehicle’s rigid frame and the movement of the wheel and
suspension assemblies.

Pressure-Control Valves. Older and a few newer vehicles depended on metering and
proportioning vales to control braking application. Metering and proportioning valves
were used to modulate hydraulic pressure to front disc or rear drum brakes to provide
smooth brake application and reduce the tendency to lock the rear brakes. Although
An ABS is a service there are many vehicles on the road that use metering and proportioning valves, on
brake system that
modulates hydraulic most newer vehicles, ABS and stability control replaces the need for using mechanical
pressure to one or more control valves. Although some systems retain proportioning valves for use in the event
wheels as needed to that the ABS system fails, most are no longer in use. Metering valves, which slowed the
keep those wheels from
locking during braking. If
application of the front disc brakes to allow the drum brakes to apply, have been less
the wheel locks during common since most late model vehicles have disc brakes in both front and rear. Older
braking, steering control vehicles had a pressure differential switch that was used in some systems to turn on the
becomes very difficult. instrument panel warning lamp if half of the hydraulic system loses pressure. Today’s
ABS allow the driver to
maintain control of the systems use a fluid level switch to detect the loss of fluid in the system, in addition to
vehicle during a panic the ABS system, which can be utilized to detect problems in the hydraulic braking
stop. systems as well.
As was noted earlier, even though pressure-control valves have been part of brake
systems for more than 60 years, ABS and stability-control systems are beginning to
Dynamic rear
proportioning and
make some valves obsolete. An ABS electronic control module can modulate hydraulic
electronic brake pressure for normal braking better than metering and proportioning valves can. As ABS
distribution are names installations became standard equipment, some older hydraulic functions have been given
for the electronic over to the electronic modulator. The electronic function of the proportioning valve has
function of the
proportioning valve by been called “dynamic rear proportioning” and “electronic brake distribution” by
the ABS braking system. various manufacturers.
Wheel Cylinders and Caliper Pistons. The wheel cylinders of drum brakes and the
The increasing use of caliper pistons of disc brakes operate in response to the master cylinder. These hydraulic
four-wheel disc brake cylinders at the wheels change hydraulic pressure back into mechanical force to apply the
systems instead of the brakes.
front disc/rear drum
systems has also
Most systems with drum brakes have a single, two-piston cylinder at each wheel
reduced the need for (Figure 1-14). Hydraulic pressure enters the cylinder between the two pistons and forces
metering valves. them outward to act on the brake shoes. As the shoes move outward, the lining contacts
the drums to stop the car. Wheel cylinder construction and operation of drum brakes are
covered in Chapter 8 of this manual.
A wheel cylinder is the
hydraulic cylinder The caliper pistons for disc brakes also act in response to hydraulic pressure that
mounted on the backing enters a fluid chamber in the caliper. Hydraulic pressure in a stationary caliper is applied
plate of a drum brake to one or two pistons on each side of the caliper to force the pads against the rotor, as
assembly.
shown in Figure 1-5. Pressure is applied to a single piston in a movable caliper on the

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 Brake System Fundamentals 11

Brake drum

Piston
Piston
Wheel Hydraulic
cylinder pressure

Brake shoes

Figure 1-14 Hydraulic pressure in the wheel cylinder moves the two pistons
outward to force the shoes against the drum.

inboard side to force the inboard pad against the rotor. As explained later, in Chapter 2,
hydraulic pressure is equal in all directions in a sealed chamber. This equal pressure cre-
ates a reaction force that moves the outboard side of the caliper inward so that both pads
grip the rotor, as shown in Figure 1-6. More details about caliper construction and opera-
tion of disc brakes are found in Chapter 7 of this manual.

Power Boosters
Almost all brake systems have a power booster that increases the force of the driver’s foot
on the pedal (Figure 1-15). Most cars and light trucks use a vacuum booster that uses the
combined effects of engine vacuum and atmospheric pressure to increase pedal force. Some

Figure 1-15 The power brake booster increases the brake pedal force
applied to the master cylinder.

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 12 Chapter 1

vehicles without a ready vacuum source may have a hydraulic power booster that may be
supplied with fluid by the power steering system or that may be a part of the brake system
and driven by an electric motor. Alternatively, as was discussed earlier, the brake actuator
can amplify the brake pressure applied to the wheel calipers based on input from the brake
stroke sensor. Chapter 6 in this Classroom Manual explains power boosters in detail.

Parking Brakes
After the service brakes stop the moving car, the parking brakes help to hold it stationary.
Parking brakes are mistakenly called “emergency” brakes, but their purpose is not to stop
the vehicle in an emergency. The amount of potential stopping power available from park-
ing brakes is much less than from the service brakes. Because the parking brakes work on
only two wheels or on the driveline, much less friction surface is available for braking
energy. In the rare case of total hydraulic failure, the parking brakes can be used to stop a
moving vehicle, but their application requires careful attention and skill to keep the vehicle
from skidding or spinning.
Parking brakes on most cars and light trucks are applied with cables. On rear drum
brakes, the brakes’ shoes are applied by the cable pulling a shoe into the drum. On some
rear disc brakes, a cable applies the caliper mechanically, while most late model disc park-
ing brakes are applied by a small set of brake shoes that sit inside a special brake rotor on
the rear wheels. In either case, the parking brake shares the components of the disc and/
or drum braking systems. Some parking brakes are applied through the use of an electric
motor on the calipers instead of a cable, and some parking brakes use an electric motor
to apply tension to the brake cables, but the basic concept is still the same.

traction control Electronic Braking Systems

systems are designed to Electronic braking covers all systems from ABS and traction-control systems (TCSs) up
prevent wheel slip in
low-traction situations to and including vehicle stability control (VSCs). While there are different terms used
by applying the brakes by the various manufacturers for the same operation, all operate with electronic sensors
to the free spinning and actuators with little or no input from the vehicle operator. Some systems such as VSC
wheel.
are in the second and third stages of development and application. The National Highway
Traffic Safety Administration (NHTSA) mandated VSC for all models built after 2012.
vehicle stability control Now we are seeing additional developments, such as cruise control that reacts to traffic
is an electronic assisted conditions, blind spot detection, lane departure alerts, and parking assist.
braking system that can
selectively apply and Whenever the brakes are applied with heavy pressure, the wheel may totally stop
release brakes during rotating. This condition is called wheel lockup or negative wheel slip, which does not
critical maneuvers to help the car stop. Rather, the tire loses some frictional contact with the road and slides or
help the driver maintain
control.
skids. As the tires slide, the car is no longer stopping under control, and the driver is in a
dangerous situation. Experienced drivers try to prevent wheel lockup by pumping the
brake pedal up and down rapidly. This stops and starts hydraulic pressure to the brakes
Lockup or negative
wheel slip is a condition
and gives the driver control during hard braking.
in which a wheel stops All late-model cars have an ABS. The ABS does the same thing as an experienced
rotating and skids on driver would, only it does it faster and more precisely. It senses when a wheel is about to
the road surface. lock up or skid. It then rapidly interrupts the braking pressure to the brakes at that wheel.
Speed sensors at the wheels monitor the speed of the wheels and send this information
ABS prevents tires from to an on-board computer. The computer then directs the ABS unit to pulse the pressure
skidding during braking. going to the wheel that is starting to lock up.

Positive wheel spin Traction-Control Systems (TCS)

happens with no
traction and the wheel The TCS controls wheel spin or positive wheel spin during hard acceleration or slippery
spins but does not move road conditions. The TCS has some options to control wheel spin. It can reduce engine
the vehicle.
power via the throttle actuator control (TAC), reduce engine timing through the ECM,

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 Brake System Fundamentals 13

and apply the brakes to the spinning wheel. This allows the torque to be transferred to the Throttle actuator control
wheel, which has traction, allowing the vehicle to move. is electronic control of
the throttle by electric
Automatic Ride Control motor instead of a
conventional throttle
Automatic Ride Control (ARC) is an electronic suspension system designed to provide a cable.
more comfortable ride to the passengers and allow better control of the vehicle during
cornering. To some extent, it can command reduced engine power, thereby slowing the Automatic ride control
vehicle. The major component shared between ARC and active braking is the yaw sensor. is a suspension system
that can be electrically
Active braking systems take the data from shared components, perform certain cal- tailored to supply
culations, and apply the brakes without any driver input at all. There are more details on optimum passenger
active braking and stability control in Chapter 10. comfort and cornering
ability action in a wide
range of road surfaces.
Vehicle Stability Control
Vehicle stability control (VSC) will be covered more in depth in later chapters, but a
Shared components
brief overview is given here to help you understand how all these systems interact. VSC among ABS and TCS are
is the result of advances in technology that is expected to save many lives, in particular by the wheel speed sensors
preventing single vehicle crashes due to loss of driver control. VSC systems depend on a and hydraulic modulator.
vehicle responding to the application of the brakes to help control the vehicle that is in a
skid. Like steering a bulldozer by locking the treads on the right or left sides, a vehicle with TCS is an outgrowth of
the brakes applied individually on one side can help steer the vehicle into control from a the ABS.
skid. The yaw or lateral accelerometer determines the direction and speed at which the
vehicle is skidding so the VSC can apply the appropriate wheel brake(s) to correct the skid. Lateral accelerometer
determines the direction
The direction the driver is trying to steer is determined by the steering wheel position and speed at which the
sensor, which is also a factor in the VSC decision on brake(s) application. The VSC can vehicle is skidding.
also determine if a wheel is slowing down too quickly or speeding up too fast by compar-
ing it to the other wheels by use of the wheel speed sensors (WSS) and apply TCS or
Steering wheel position
ABS braking at the appropriate times. sensor determines
which direction the
Active Braking driver is trying to steer.

Mass-produced active braking systems are systems that can act to prevent a collision with-
out input from the driver. In the context here, “active” means the brake system will perform Wheel speed sensors
are mounted at selected
some functions without input from the operator. The ABS could be considered as the first (or all) wheels to
active braking system, but it functioned only if the driver had applied the brakes and if certain monitor wheel speed
conditions, such as wheel skid, were present. The active braking systems of today use com- during vehicle operation.
ponents from the ABS, TCS, VSC, and radar or cameras to determine how close the vehicle
is to another vehicle or an obstruction. Most systems warn the driver of an impending col- Yaw is the deviation in
the line of travel
lision. If the driver does not respond, then the braking system acts on its own to bring the commonly referred to as
vehicle to a stop, or at least reduce the severity of a collision if it cannot come to a complete roll or lean during
stop. Each of the systems listed normally has its own controller or computer module. cornering.

Active braking systems

TRAILER BRAKES can apply the brakes
without the driver
touching the brake
Normally a textbook of this type does not deal with trailer brakes. However, with the pedal. Meant to be used
advent of active braking systems and the increasing sales and usage of ¾- and 1-ton pick- during an emergency
ups, it is important that some information is provided. Consult local and state laws for stop.
specific requirements.
Older trucks used to tow trailers heavy enough to warrant a brake system always used
an add-on system. This system was not efficient in some cases, and its efficiency in many
cases was based on “you got what you paid for.” If the trailer was lightly loaded or the road
was slick, the trailer brakes could lock and the trailer would probably jack-knife. Heavy
trucks over 1 ton did have a trailer brake system that was either “hard-wired” at the factory

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 14 Chapter 1

or at least had to meet stringent Department of Transportation (DOT) standards. The

newest ¾- and 1-ton truck models offer a factory-installed trailer brake system. This sys-
tem borrows from the ABS and active braking systems. Trailer brake systems are usually
divided into two types: hydraulic surge and electric.

Hydraulic Surge
A hydraulic surge brake system is completely mounted on the trailer. It may be a disc or drum
type and operates hydraulically and mechanically in a very similar manner to the drum brakes
on the tow vehicle. There is a pressure differential valve mounted somewhere in the tow
vehicle’s rear brake system, usually at or near the vehicle’s master cylinder. This valve operates
so the pressure supplied to the trailer’s master cylinder is in direct proportion to the pressure
being directed to the tow vehicle’s rear brake. The valve works very similarly to the regular
proportioning valve found on almost every roadworthy vehicle. The pressure delivered to the
trailer’s master cylinder applies a mechanical pushrod, which, in turn, creates the correct
pressure to apply the trailer brake. Trailer drum brakes may be uni-servo with one wheel
cylinder and one pushrod or duo-servo with one wheel cylinder and two pushrods. The uni-
servo type is the most common because of lower cost compared to the duo-servo system.
The disc-brake type operates almost exactly like the disc brakes on a standard vehicle.

Electric Brakes
Electric trailer brakes are most commonly used on utility and RV units, whereas boat trail-
ers or others that are designed to be submerged underwater use the hydraulic surge. This
is because water severely shortens the life expectation of electric brake components.
A trailer electric brake system requires a brake controller mounted in the tow vehicle
within hand control of the vehicle driver. It is usually mounted on the dash near the steer-
ing column (Figure 1-16). The driver may reduce or increase the power of the trailer
brakes or lock them down as a kind of parking brake. The controller is not readily switched
between different tow vehicles, so each tow unit must be equipped with its own controller.
There are three types of controllers, but each performs basically the same function. For
detailed information on the controllers and troubleshooting trailer brakes, investigate
Champion Trailers at its website at http://www.championtrailers.com/techsup.html. The
regulated electric power from the controller is sent to magnets within the wheel drum.
The energized magnets are pulled toward a specially machined flat surface of the drum.
As the magnets move, they, in turn, move a lever or levers attached to the brake shoe. The

Figure 1-16 This is a typical add-on trailer brake controller.

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 Brake System Fundamentals 15

brake shoe is applied against the rotating drum in direct proportion to the braking action
of the rear brakes of the tow vehicle.

Trailer Breakaway Condition

The DOT requires any trailer with its own braking system to have a method to apply its
brakes in case the trailer disconnects from its tow vehicle. On an electric system, an emer-
gency power battery is mounted on the trailer. If a breakaway condition occurs, the pull
pin at the trailer/vehicle hitch is pulled loose, triggering a switch that connects the full
power of the emergency battery to the wheel magnets. This effectively locks the wheels.
The hydraulic surge system uses a slightly different method to accomplish the same result.
A chain or cable runs from the tow vehicle to a lever positioned to apply force to the piston
in the trailer’s master cylinder. When a disconnect situation occurs, the lever is moved by
the chain/cable and applies the trailer brakes. In either case, both breakaway systems may
be used as parking brakes when the trailer is stored or being loaded/unloaded.

Reverse Braking
Trailer brakes do not recognize reverse braking from forward braking. Usually it is best if
the trailer does not have braking during reverse operation. To prevent this, the hydraulic
surge brake may be standard or free backing (Figure 1-17). The standard type requires a
reversing solenoid that is triggered when the tow vehicle backup lights are activated
(Figure 1-18). The solenoid is plumbed into the system at the outlet of the trailer’s master
cylinder. With the solenoid energized, pressurized fluid from the master cylinder is
blocked from the wheels and is directed back into the master cylinder’s reservoir. Free
backing operation recognizes that the wheels are rotating backward and deactivates the
brakes. The brake system reactivates when the wheels rotate forward. This is the system
of choice for most trailers because it can be manufactured into the system. It should be
noted that disc brakes on trailers must have a free backing (reversing) solenoid. Electric
brake systems use only a reverse solenoid to prevent the trailer brakes from functioning
in reverse. The solenoid is triggered by the backup lights circuit.

Author’s Note Technicians or do-it-yourselfers can get into difficulties if they

do not understand how to connect an add-on trailer brake system. Also, if the
­add-on system is on the less expensive side, the rule “you get what you pay for”
applies. There are some add-on units that meet DOT standards but have no
­leeway if the trailer is loaded or too heavy for the brake system.

Standard Free backing

Figure 1-17 The free backing brake on the right recognizes reverse movement and the
brake cannot be applied.

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 16 Chapter 1

Brake fluid
reservoir

Fluid return line

To brake switch

To wheel
cylinders

Reversing
solenoid Trailer
master
cylinder

Figure 1-18 The reversing solenoid is needed with the standard brakes in
Figure 1-15 to prevent braking in reverse.

Before installing an add-on system, read the specifications carefully, and talk to the
customer about the weight and number of axles on the trailer. On multiple-axle trailers,
braking components may be installed at each wheel or only on one axle. The total weight
of the loaded trailer, not just the payload of one axle, must be considered when selecting
the capacity of the braking system.

Author’s Note This short section on air brakes is to give an overview to the
reader should he or she end up working for a fleet or having to provide some type
of emergency assistance to an air brake–equipped vehicle. Remember that more
in-depth training will be required to provide air brake maintenance and repair. Air
brake systems must comply with DOT requirements and inspection procedures.

Air Brakes
Air brakes are brakes Air brakes require at least 100 psi to operate correctly. This pressure is provided by a
applied by using belt-driven air compressor, and the compressed air is held in one or two air reservoirs
compressed air. Only (tanks). A governor mounted on the compressor limits the amount of pressure to about
used on heavy-duty
trucks.
125 psi. The reservoirs and the brakes are connected via steel tubing to a manifold valve
(foot valve) usually mounted on the engine side of the bulkhead. A three-way valve directs
the air dependent on the action of the driver.
The wheel brake friction components, drum or disc, are actually applied by a spring-
operated diaphragm within a brake chamber at each wheel. The diaphragms are held off
(brakes released) by air pressure on the brake side of the diaphragm. Slack adjusters are
placed between the chamber pushrod and the S-cam in the wheel brake mechanism. Slack
adjusters allow the operator or technician to adjust the brakes for wear and are one of the
first items checked during a DOT inspection.
When the brakes are applied, some portion of the air pressure retaining the diaphragm
is released, and the spring pushes the diaphragm, thereby moving the pushrod
(Figure 1-19). The pushrod in turn rotates the S-cam and applies a proportional amount
of movement to the brake shoes in relation to the amount of air released. A red button on
the dash labeled PARK applies the parking brakes by releasing all of the air in all of the

64533_ch01_hr_001-019.indd 16 1/31/18 10:39 AM

 Brake System Fundamentals 17

Pushrod
Slack
adjuster

Air
chamber

AXLE SIDE

Brake released Brake applied

S-cam

Drum

WHEEL SIDE
Brake shoe Anchor

Figure 1-19 The S-cam is rotated by actions of the air chamber. As the “S” turns, the wings of the “S” push the brake
shoe outward.

brake chambers. Anytime the vehicle is parked, the parking brakes should be engaged. On
the steering column is a lever that allows the driver to apply only the trailer brakes from
full lock to a moderated braking effect. The hissing noise commonly heard around air
brake vehicles is from brakes being applied, parking brakes being applied, or a release of
excess pressure from the air reservoirs.
When the tractor is attached to a trailer, two flexible air lines connect the tractor and
trailer brakes. A tractor protection valve is located on the tractor to prevent a loss of
brakes on the tractor if the trailer brake system develops a leak or becomes disconnected.
The lines extending from the tractor are self-sealing while the connections on the trailer
side are not. When the hoses are disconnected, the trailer brakes lock down (park mode).
Although this overview does not provide sufficient information to become an air
brake technician, there is still enough information for the average automotive technician
to make a quick safety inspection. With the system fully charged at 100 psi or more, shut
down the engine and perform a walk-around inspection. Any hissing sound at this time
usually denotes an air leak, and the leak can be traced by following the sound. At this point
in your training, do not attempt a repair. Notify a trained heavy truck technician of your
findings. If the air pressure does not reach 100 psi, there are several devices that can cause
this problem, and repairs are best left to a properly trained technician.

64533_ch01_hr_001-019.indd 17 1/31/18 10:39 AM

 18 Chapter 1

SUMMARY
■■ An automotive brake system consists of a master ■■ Active braking systems may function with or
cylinder and control valves connected hydraulically ­without driver input.
through lines to disc and drum brake units that ■■ Vehicle stability control systems share
stop the wheels. components with the ABS, TCS, and
■■ A hydraulic or vacuum power assist is used on ARC to provide better vehicle control and
most cars to decrease the braking effort required comfort.
from the driver. ■■ Trailer brakes may now be controlled or regulated
■■ A stroke sensor is used to tell the brake actuator how by components similar to those used in active
fast and how far the driver applied the brake pedal. ­braking systems.
■■ A stroke simulator is used to give the driver a ■■ Air brake systems use compressed air to control
­normal pedal feel. the movement of a diaphragm.
■■ A mechanical brake, operated by levers and cables, ■■ Regardless of the type of braking system,
is used for parking. ­mechanical, hydraulic, or electronic, the final
■■ All late model cars have an ABS to improve brake ­braking action occurs between the tire and the
operation during emergency stopping. road.

REVIEW QUESTIONS
Short-Answer Essays
1. Name the four basic functions of the braking 6. Describe regenerative braking.
system. 7. Describe the lines and hoses used on vehicle
2. Briefly describe the modern master cylinder. braking systems.
3. Briefly describe why the split system is needed on 8. Why is it wrong to call the parking brake an
modern vehicles. “emergency brake.”
4. Describe the purpose of the brake stroke sensor 9. Describe what is meant by negative wheel slip.
on a hybrid vehicle. 10. Explain how the traction control system works to
5. Describe the two types of split hydraulic systems. control wheel spin.

Fill in the Blanks 6. All master cylinders for vehicles built since 1967
have _______________ _______________ and
1. _______________ braking systems use electrical
pumping chambers
generators to help slow the vehicle during gradual
stops and help recharge the electric batteries. 7. There are two types of split systems:
_______________ and front/rear.
2. The _______________ _______________ is
mounted on a lever with a pivot near the top of 8. The electronic function of the proportioning
the lever. valve has been called “_______________
_______________ _______________” and
3. Modern automotive _______________ “_______________ _______________
_______________were developed from aircraft _______________” by various manufacturers.
brakes of World War II.
9. Most systems with drum brakes have a single,
4. Disc _______________ _______________ are mounted _______________ cylinder at each wheel.
in a caliper that sits above the spinning rotor.
10. The ABS does the same thing as an
5. The _______________ _______________ is the _______________ _______________ would, only it
start of the brake hydraulic system. does it faster and more precisely.

64533_ch01_hr_001-019.indd 18 1/31/18 10:39 AM

 Brake System Fundamentals 19

Multiple Choice 6. Technician A says that all new vehicles have

metering and proportioning valves. Technician B
1. Technician A says all the friction components of a
says that the function of these valves has been
disc brake are exposed to the airstream. Technician
taken over by the ABS system on most vehicles.
B says this helps to cool the brake parts and
Who is correct?
­maintain braking effectiveness during repeated
hard stops from high speeds. Who is correct? A. A only C. Both
A. A only C. Both B. B only D. Neither
B. B only D. Neither 7. While discussing wheel cylinders and caliper
­pistons, Technician A says wheel cylinders of
2. Technician A says that with a fixed caliper, drum brakes operate in response to the master
hydraulic pressure is applied to pistons on both cylinder. Technician B says the caliper pistons of
sides to force the pads against the rotor. disc brakes operate in response to the wheel cyl-
Technician B says that with a movable caliper, inders. Who is correct?
pressure is applied to a piston on the outboard
A. A only C. Both
side only. Who is correct?
B. B only D. Neither
A. A only C. Both
B. B only D. Neither 8. Technician A says almost all brake systems have a
power booster that increases the force of the
3. Technician A says drum brakes do not develop the ­driver’s foot on the pedal. Technician B says most
mechanical servo action that you will learn about cars and light trucks use a vacuum booster that
as you study drum brakes. Technician B says drum uses the combined effects of engine vacuum and
brakes require higher hydraulic pressure and atmospheric pressure to increase pedal force.
greater force to achieve the same stopping power Who is correct?
as a comparable disc brake. Who is correct?
A. A only C. Both
A. A only C. Both
B. B only D. Neither
B. B only D. Neither
9. Technician A says some vehicles without a ready
4. While discussing the brake stroke sensor, vacuum source may have a hydraulic power
Technician A says the brake stroke sensor informs booster. Technician B says the hydraulic booster
the brake controller how fast the brake pedal is can be supplied with fluid by the power steering
being pushed down. Technician B says the stroke system or may be a part of the brake ­system and
sensor also informs the controller how much driven by an electric motor. Who is correct?
pressure the driver is applying to the brakes. A. A only C. Both
A. A only C. Both B. B only D. Neither
B. B only D. Neither
10. Technician A says automatic ride control (ARC)
5. Technician A says the stroke simulator is used to is an electronic braking system designed to
make hybrid brake application feel normal to the ­provide a more comfortable ride. Technician B
driver. Technician B says the stroke simulator is says ARC also allows betters control of the vehicle
an electrical switch for the brake lamps. Who is during cornering. Who is correct?
correct? A. A only C. Both
A. A only C. Both B. B only D. Neither
B. B only D. Neither

64533_ch01_hr_001-019.indd 19 1/31/18 10:39 AM

 Chapter 2
Principles and Theories
of Operation

Upon completion and review of this chapter, you should be able to:
■■ Discuss the conversion of energy from ■■ Discuss hydraulic principles and how
one type to another. they may be applied in a vehicle.
■■ Discuss braking dynamics. ■■ Explain the method for calculating
■■ Explain the importance of kinetic and mechanical advantage.
static frictions in brake system. ■■ Discuss how hydraulics can be used to
■■ Describe the effects of pressure, surface transmit force.
area, and friction material on producing ■■ Discuss how a hydraulic brake system
friction during braking. can produce mechanical advantage.
■■ Discuss coefficient of friction. ■■ Define and explain the basic electrical
■■ Explain why heat dissipation is impor- terms: amperes, voltage, and
tant in a braking system. resistance.
■■ Explain how work is accomplished. ■■ Explain how to use Ohm’s law to calcu-
■■ Explain how the laws of motion affect late the amount of resistance, voltage,
the design and operation of a vehicle. and current in a circuit.

Terms To Know
Adsorption Kinetic friction Rolling resistance
Ampere (A) Lining fade Static friction
Brake fade Mass Tensile force
Ceramic Mechanical advantage Thermal energy
Coefficient of friction Mechanical fade Vacuum
Force Momentum Voltage (volt)
Gas fade Ohms (Ω) Weight
Inertia Ohm’s law
Kinetic energy Perpetual energy

INTRODUCTION
No vehicle or any other device will function correctly if the laws of physics are not con-
sidered during design and manufacturing. On the other hand, there is no current technol-
ogy to make all designs meet all factors of physics. The automotive industry has performed
well in making compromises between different physics laws to design and manufacture
vehicles that work and are affordable. In this chapter, various laws of physics are discussed
so that the reader will have a basic understanding of the physical environment that the
designers, the manufacturers, the driver, and even you must overcome to operate any type
of vehicle.

20

64533_ch02_hr_020-043.indd 20 02/02/18 6:08 pm

 Principles and Theories of Operation 21

BRAKE OPERATION/CONVENTIONAL SYSTEM

Before discussing the energy and dynamics associated with braking, a review of brake
system operation is essential. This may help when trying to understand the next
sections.
When the driver decides to slow or stop the vehicle, the first action is to remove force
from the accelerator pedal. The slowing engine, in most cases, begins to slow the vehicle.
The driver then applies force to the brake pedal.
The movement of the brake pedal activates the brake power booster, which, in turn,
boosts and transmits the driver’s input force to the master cylinder pistons via pushrods
(Figure 2-1). The master cylinder pistons turn mechanical action into hydraulic action
by pressurizing the brake fluid and forcing it out through the hoses and lines to the wheel
braking components (see Chapter 5). Older vehicles use proportioning valves and meter-
ing valves. Valves between the master cylinder and wheels control the pressure and vol-
ume of brake fluid reaching the wheels. These valves do not control actual braking force,
but they mainly divide the force between the front and rear brakes for a smooth stop
without allowing the rear wheels to lock up on hard activation. At the wheels, hydraulic
pressure is converted into mechanical action and applies the last segment of the braking
mechanism. In drum brakes, this action is accomplished by the wheel cylinders, brakes
shoes, and brake drums. On disc brakes, the same action is performed by the calipers,
brake pads, and brake rotors. The antilock brake system (ABS) becomes involved only if
it senses one (or more) wheels about to lock up. The ABS can then modulate hydraulic
pressure to that wheel(s) to reduce braking effects. Most late-model vehicles use the ABS
to replace proportioning valves with hydraulic modulation of the brake pressure to pre-
vent wheel lockup. Everything told, the braking system is a straightforward and simple
concept and operation, but it is one of the more critical systems on a vehicle.

Force converted
to hydraulic
pressure

Applied
force

Hydraulic pressure converted to

mechanical action (force) at
each wheel

Figure 2-1 The energy exerted to brake a vehicle is converted from mechanical to hydraulic and back
to mechanical.

64533_ch02_hr_020-043.indd 21 1/31/18 9:42 AM

 22 Chapter 2

BRAKE SYSTEM ENERGY

All brake systems work according to a few principles or “laws” of physics, and the concept
of energy is a basic part of physical science. Energy is the ability to do work and comes in
many familiar forms: chemical energy, mechanical energy, heat energy, and electrical
energy are among the most obvious forms in all automotive systems.
A brake system converts one form of physical energy to another. To slow and stop a
Kinetic energy is the moving vehicle, the brakes change the kinetic energy of motion to heat energy through
energy of mechanical the application of friction. When the brakes change one form of energy to another, they
work or motion.
are doing work. Work is the result of releasing or using energy.

AUTHOR'S NOTE It is impossible at this time to create or destroy energy.

However, it can be converted from one form to another. The master cylinder is
one place this happens: the mechanical energy of the brake pedal is converted into
hydraulic energy in the master cylinder bore. It is later converted back to mechani-
cal energy at the wheels.

Kinetic Energy, Mass, Weight, and Speed

Kinetic energy is the energy of mechanical work or motion. When an automobile starts,
accelerates, decelerates, and stops, kinetic energy is at work. The amount of kinetic energy
at work at any moment is determined by a vehicle’s mass (weight), speed, and the rate at
which speed is changing.
The terms “mass” and “weight” can be used interchangeably to describe objects on
Mass is the measure of the surface of the Earth, but the two terms are not technically the same. Mass is a mea-
the inertia of an object surement of the number of molecules that make up an object. Weight is a measurement
or form of matter or its
resistance to of the effect of gravity on that mass. All objects have mass, from a steel brake shoe to a
acceleration; it also is quart of hydraulic fluid to the air in an air compressor. Without going too deeply into the
the molecular density of science of physics, it can be said that the greater the number of molecules in an object and
an object.
the more complex the molecules are, the greater the mass of that object and the more
dense it is. The effect of gravity on the mass of an object is that object’s weight.
The basic difference between mass and weight can be understood by thinking of the
space shuttle, which weighs about 1,000,000 pounds on the launch pad, on the Earth.
When the shuttle is in orbit, outside the Earth’s gravity, it is weightless (Figure 2-2). Its
mass stays the same, however.
The combined effects of weight and speed constitute kinetic energy, but speed has a
much greater effect than weight. The kinetic energy of any moving object can be calcu-
lated with this formula, which is quite simple:
mv 2
5 Ek
29.9

where

m 5 mass (weight) in pounds

v 5 velocity (speed) in miles per hour
Ek 5 kinetic energy in foot-pounds

Consider two cars, both traveling at 30 miles per hour (mph). One weighs 2,000
pounds; the other weighs 4,000 pounds (Figure 2-3).

64533_ch02_hr_020-043.indd 22 1/31/18 9:42 AM

 Principles and Theories of Operation 23

Weightless

In Orbit

4,000 miles

Equal mass
One million pounds Different weight

On the Earth

Figure 2-2 The space shuttle has equal mass but different weights
on the Earth and in orbit.

2,000 3 30 2
5 60,200 foot - pounds of kinetic energy for the lighter car
29.9
4,000 3 30 2
5 120, 400 foot - pounds of kinetic energy for the heavier car
29.9
Doubling the car weight doubles the kinetic energy when the speeds are equal.
Therefore, kinetic energy increases and decreases proportionally with weight. Now let us
accelerate the lighter car to 60 mph (Figure 2-4).
2,000 3 60 2
5 240,802 foot - pounds of kinetic energy for the lighter car
29.9

When the speed is doubled, kinetic energy increases not two times, but four times.
Kinetic energy increases as the square of the speed. If we accelerate the same 2,000-pound

60,200
foot-pounds
60,200 2,000 pounds of energy
foot-pounds
2,000 pounds
of energy
30 mph
30 mph

120,400
foot-pounds 240,802
4,000 pounds of energy 2,000 pounds foot-pounds
of energy
30 mph
60 mph
Figure 2-3 Kinetic energy increases proportionally with vehicle
weight. Figure 2-4 Kinetic energy increases exponentially with vehicle speed.

64533_ch02_hr_020-043.indd 23 1/31/18 9:42 AM

 24 Chapter 2

car to 120 mph, its kinetic energy is 16 times greater than it was at 30 mph—almost
1,000,000 foot-pounds.
Remember the brake performance test described in Chapter 1 of the Shop Manual,
in which the required stopping distance at 30 mph was 57 feet, but increased to 216 feet
at 60 mph. That is a practical example of kinetic energy at work. The effects of kinetic
energy are also why a high-performance car needs a brake system with much greater stop-
ping power than an economy car with only modest performance.

Inertia and Momentum

Inertia is the tendency When a car is accelerated and then decelerated and brought to a stop, two forms of inertia
of an object in motion are in play. Inertia is simply the resistance to a change in motion. An object at rest tends
to keep moving and the
tendency of an object at to remain at rest; an object in motion tends to remain in motion. In both cases, the object
rest to remain at rest. resists any change in its motion.
Static inertia is the inertia of an object at rest; dynamic inertia is the inertia of an
object in motion. When the brake system slows and stops a vehicle, it overcomes dynamic
inertia and imposes static inertia. The brake system also must overcome the vehicle’s
Momentum is the force momentum. Momentum is another way to view kinetic energy at work because it, too,
of continuing motion; is the mathematical product of an object’s mass times its speed. Physical force starts an
the momentum of a
moving object equals its
object in motion and gives it momentum. Another kind of force must overcome the
mass times its speed. momentum to bring the object to a stop. That force is friction.

BRAKING DYNAMICS
One important brake system dynamic is called weight transfer. You have probably had the
experience of applying the brakes hard for an emergency stop. During such a stop, the
front of the car lowered and you could feel yourself being thrown forward against your
seat belt. This is caused by the vehicle weight being transferred from the rear to the front
during braking, which means that more of the braking must be done by the front wheels
and less by the rear wheels.

AUTHOR'S NOTE When the driver applies the brakes, the vehicle—not the
driver or the passengers—is being slowed. Without seat belts and air bags, the
vehicle occupants tend to keep moving in the same direction and at the same
speed of the vehicle as before the brakes were applied. Hence, the use of safety
restraints is required to reduce injuries.

The weight of a car is not distributed evenly on all four wheels even when the vehicle
is standing still. The position of the heavy engine and powertrain components determines
weight distribution. During braking, the weight of these components transfers forward.
On a rear-wheel-drive car, about 70 percent of the weight shifts to the front. On a front-
wheel-drive car, as much as 90 percent of the car weight is shifted to the front during
braking. The vehicle’s momentum and weight combine to cause the rear wheels to lift
(have less down force applied) and the front wheels to be forced down (Figure 2-5).
Therefore, front brake systems are larger than rear units.
Another dynamic to think about is braking power. As the previous section of this
chapter about kinetic energy explained, the more the car weighs and the faster it is mov-
ing, the greater the braking power must be to stop the car. The brake system is designed
with more power than the engine. Consider a typical car with a 200-hp engine. This car
can accelerate from 0 to 60 mph in 10 seconds. The brake system must be able to

64533_ch02_hr_020-043.indd 24 1/31/18 9:42 AM

Another Random Scribd Document
with Unrelated Content
 Entre esta gente de la ropa nívea, dos tipos llamaron
especialmente mi atención: eran padre e hijo. El
primero, de unos treinta años, de atlética estatura, era
ladrón nocturno, famoso por su habilidad en el oficio.
Hallábase preso por una muerte atroz, perpetrada, a
favor de una noche silenciosa, en una casa de
Carabanchel, donde tuvo por único cómplice a su hijo,
un niño de menos de siete años de edad. «La manzana
—como dice Dauer—no ha caído lejos del árbol.» El
retoño era en un todo un traslado de su padre, aunque
en miniatura. Llevaba también las mangas de seda, el
chaleco con botones de plata y el pañuelo rodeado a la
cabeza, como los ladrones, y, cosa bastante ridícula, un
enorme cuchillo manchego en la faja carmesí. Con toda
evidencia, era el orgullo del rufián de su padre, que
atendía con todos los cuidados imaginables a aquella
cría de la horca; le columpiaba en sus rodillas, y a veces
se quitaba el cigarro de sus labios bigotudos para
ponérselo en la boca al pequeñuelo. El chico era el
favorito del patio, porque su padre era uno de los
valientes de la cárcel, y los que temían sus proezas y
deseaban serle agradables estaban siempre mimando a
su hijo. ¡Qué enigma es este mundo! ¡Qué obscuras y
misteriosas las fuentes de lo que llaman crimen y virtud!
Si aquel desventurado niño es, con el tiempo, un
asesino como su padre, ¿podría culpársele por ello?
Arrullado por ladrones, ya vestido de ladrón, hijo de un
ladrón cuya historia fué quizás igual a ésta, ¿es justo...?
¡Oh hombre! ¡Hombre! No intentes penetrar en el
misterio del bien y del mal morales; reconoce que eres
un gusano, arrójate al suelo y murmura con los labios
pegados al polvo: ¡Jesús! ¡Jesús!
Lo que más me sorprendió fué el buen
comportamiento de los presos; lo llamo bueno después
de considerar bien todas las cosas y de compararlo con
el de la generalidad de los presos en otros países.
Tienen en ocasiones sus estallidos de alegría salvaje,
sus riñas, que habitualmente ventilan en el segundo
patio cuchillo en mano; el resultado suele ser con
frecuencia una muerte, o algún desgarrón espantoso en
la cara o en el abdomen; pero, en general, su conducta
era infinitamente superior a lo que podía esperarse de
los huéspedes de tal lugar. Sin embargo, no era el
resultado de la coacción, ni de vigilancia alguna especial
que se ejerciese sobre ellos, pues quizás en ninguna
parte del mundo están los presos tan abandonados a sí
mismos y en tan extremado descuido como en España:
las autoridades no se preocupan más que de impedir su
fuga; no prestan la más mínima atención a su conducta
moral, ni consagran un solo pensamiento a su salud,
comodidad o mejoramiento mental mientras los tienen
encerrados. Con todo, en esta cárcel de Madrid, y
puede decirse que en las prisiones españolas en
general, pues he sido huésped de más de una, los oídos
del visitante no se sienten nunca lastimados con las
horrendas blasfemias y obscenidades que se oyen en
las cárceles de otros países, especialmente en las de la
civilizada Francia; ni ofendidos sus ojos e insultado
personalmente, como lo sería de seguro en Bicêtre al
querer mirar al patio desde las galerías, y eso que en la
cárcel de Madrid se hallaban tipos de lo más perdido de
España, rufianes que tenían a su cargo atrocidades y
crueldades espeluznantes. Pero la gravedad y la calma
son los caracteres que predominan en los españoles; y
hasta el ladrón, salvo en los instantes en que está
entregado a sus faenas (y entonces no le hay más
sanguinario, más despiadado ni más rapaz y ansioso de
botín), puede ser hombre cortés y afable, que gusta de
conducirse con templanza y decoro.
 Felizmente para mí, quizás, mi conocimiento con los
rufianes de España comenzó y acabó en las ciudades
por donde anduve y en las prisiones en que fuí arrojado
por la causa del Evangelio, y, a pesar de mis frecuentes
viajes, nunca me los encontré en los caminos ni en
despoblado.
El preso de peor genio en toda la cárcel, y también
probablemente el más notable, era un francés como de
sesenta años, de estatura regular, pero delgado, como
casi todos sus compatriotas. La hechura del cráneo
delataba, para un frenólogo, la vileza del sujeto; sus
facciones tenían muy dañada expresión. No llevaba
sombrero, y sus vestidos, aunque parecían casi nuevos,
eran de lo más ordinario. Por lo general manteníase
apartado de los demás, y se pasaba horas enteras de
pie recostado en las paredes, con los brazos caídos,
mirando con ojos de mal humor a cuantos pasaban por
delante. No figuraba entre los valientes de profesión de
la cárcel: su edad no le permitía ya asumir tan eminente
calidad; pero todos los demás presos parecían tratarle
con cierto temor: quizás temían su lengua, pues, en
ocasiones, empleábala en verter maldiciones horrendas
sobre los que incurrían en su desagrado. Hablaba a la
perfección en buen español y, con gran sorpresa mía,
en excelente vascuence, y en esta lengua conversaba
con Francisco, quien, asomándose a la ventana de mi
cuarto, bromeaba con los presos del patio, que le tenían
en gran aprecio.
Un día, estando en el patio, donde por permiso del
alcaide podía entrar cuando quería, me acerqué al
francés, que estaba, como de costumbre, recostado en
la pared, y le ofrecí un cigarro. Yo no fumo, pero no
debe uno mezclarse con las clases bajas de España sin
llevar un cigarro que ofrecer llegado el caso. El hombre
me miró con ferocidad un instante, y, al parecer, iba a
rechazar mi obsequio con una horrible maldición quizás.
Repetí el ofrecimiento, sin embargo, llevándome la
mano al corazón, y en el acto sus torvas facciones se
dilataron, y con un gesto genuinamente francés, y una
profunda cortesía, aceptó el cigarro, exclamando:
—Ah, monsieur, pardon, mais c’est faire trop
d’honneur à un pauvre diable comme moi.
—Nada de eso—repliqué—. Los dos estamos presos
en tierra extranjera y, por tanto, debemos protegernos
mutuamente. Supongo que siempre que necesite su
ayuda de usted en la cárcel podré contar con ella.
—Ah, monsieur—exclamó el francés transportado—,
vous avez bien raison; il faut que les étrangers se
donnent la main dans ce... pays de barbares. Tenez—
añadió en voz baja—si tiene usted algún plan para
escaparse, y necesita de mí, cuente con un brazo y un
cuchillo a su servicio; puede usted fiarse de mí: no
espere tanto de ninguna de esas sacrées gens d’ici—. Al
decir esto echó una rabiosa mirada sobre sus
compañeros de cárcel.
—No me parece usted muy amigo de España ni de
los españoles—dije yo—. Deduzco que han cometido
con usted alguna injusticia. ¿Por qué está usted en la
cárcel?
—Pour rien du tout, c’est à dire pour une bagatelle;
pero ¿qué puede esperarse de estos animales? ¿No le
han encarcelado a usted, según he oído, por brujería y
gitanismo?
—¿Quizás le han traído aquí por sus opiniones?
 —Ah mon Dieu, non; je ne suis pas homme à
semblable betise. Yo no tengo opiniones. Je faisois...
mais ce n’importe; je me trouve ici, où je crève de faim.
—Siento ver a un buen hombre en situación tan
calamitosa—dije yo—. ¿No tiene usted para vivir algo
más que la ración de la cárcel? ¿No tiene usted amigos?
—¿Amigos en este país? Se burla usted de mí. ¡Aquí
no encuentra uno amigos, a menos que los compre!
¡Reviento de hambre! Desde que entré aquí he ido
vendiendo mi ropa, hasta quedarme desnudo, para
comer, porque la ración de la cárcel no basta para el
sustento, y aún nos roba la mitad el Batu, como llaman
al bárbaro del gobernador. Les haillons que ahora me
cubren me los han dado unas señoras devotas que
algunas veces nos visitan. Los vendería si valiesen algo.
No tengo un sou, y por falta de unos cuantos duros me
ahorcarán dentro de un mes si no logro escaparme,
aunque, como ya le dije antes, no he hecho nada: una
simple bagatela; pero en España no hay peores
crímenes que la pobreza y la miseria.
—Le he oído a usted hablar en vascuence. ¿Es usted
de la Vizcaya francesa?
—Soy de Bordeaux, monsieur; pero he vivido mucho
tiempo en las Landas y en Vizcaya, travaillant à mon
metier. Leo en sus ojos que desea usted conocer mi
historia; no se la cuento; no contiene nada de particular.
Vea usted, ya me he fumado el cigarro; deme usted
otro, y un duro de añadidura, si me hace el favor, nous
sommes crevés ici de faim. A un español no le diría
tanto; pero sus compatriotas de usted me inspiran
respeto; los conozco bien; he tropezado con ellos en
Maida y en el otro sitio[13].
 ¡Nada de particular en su historia! Mucho me
engaño, o un solo capítulo de su vida, de haberse
escrito, hubiera contenido más peripecias maravillosas
que cincuenta volúmenes de aventuras por tierra y mar
de las que más arriesgadas parezcan. Había sido
soldado. ¡Qué de cosas no podría contar aquel hombre
de marchas y retiradas, de batallas perdidas y ganadas,
de ciudades saqueadas, conventos allanados! Quizás
había visto las llamas de Moscou subir hasta las nubes,
y «había medido sus fuerzas con las de la Naturaleza en
el desierto invernal», asaltado por las borrascas de
nieve y mordido por el tremendo frío de Rusia. ¿Y qué
podía significar con lo de ejercer su oficio en Vizcaya y
en las Landas, sino que había sido ladrón en esas
regiones agrestes, la segunda de las cuales es, por los
robos y crímenes que en ella se cometen, la peor
reputada de todo el territorio francés? ¿Nada de
particular en su historia? Entonces, ¿qué historia tendrá
algo que valga la pena de ser contado?
Di al preso el cigarro y el duro. Se los guardó, y
dejando caer nuevamente los brazos, y recostándose en
la pared, pareció hundirse poco a poco en uno de sus
ensimismamientos. Le miré a la cara y le hablé; pero no
pareció oírme ni verme. Su espíritu erraba quizás en el
pavoroso valle de la sombra, hasta el que se abren
camino a veces, durante su vida, los hijos de la tierra;
pavoroso lugar donde no hay agua, ni mora la
esperanza, ni vive más que el gusano imperecedero del
remordimiento. Ese valle es un facsímil del infierno, y
quien penetra en él sufre aquí en la tierra
temporalmente lo que las almas de los condenados han
de sufrir a través de las edades sin fin.
El francés fué ahorcado un mes más tarde. La
bagatela por que estaba preso eran varios robos y
asesinatos cometidos mediante una singular
estratagema. De concierto con otros dos, alquiló una
vasta casa en un barrio poco frecuentado, y a ella
mandaba que le enviasen géneros de valor que
compraba en los comercios para pagarlos en el
momento de la entrega, y los que iban a entregar
pagaban su credulidad con la pérdida del género y de la
vida. Dos o tres cayeron en el lazo. Tuve vivos deseos
de hablar privadamente con aquel hombre tan arrojado,
y, por tanto, rogué al alcaide que le permitiera comer
conmigo en mi cuarto; a esto, el gobernador, a quien
me tomaré la libertad de llamar monsieur Bassompierre,
por habérseme olvidado su verdadero nombre, se quitó
el sombrero, y con sus habituales sonrisa y reverencias
me replicó en el más puro castellano:
—Caballero inglés, y creo que puedo añadir, amigo
mío: perdóneme usted, pero me es del todo imposible
acceder a su petición, fundada, no lo dudo, en los más
admirables sentimientos de filosofía. A otro cualquiera
de estos caballeros que están bajo mi custodia se le
permitirá, cuando usted lo desee, acompañarle en su
cuarto. Incluso llegaré a mandar que le quiten los grillos
al que haya de ir con usted, si tuviese grillos puestos, a
fin de que pueda participar en la comida de usted con la
comodidad y holgura convenientes; pero con el
caballero de que se trata no puedo consentirlo: es el
peor de toda esta familia, y seguramente en la
habitación de usted o en la galería armaría una función
para intentar fugarse. Caballero, me pesa; pero no
puedo acceder a lo que pide. Si se tratase de otro
caballero cualquiera, lo haría con mucho gusto; el
mismo Balseiro, a pesar de lo que de él se cuenta, sabe
conducirse como es debido; en su modo de proceder
hay siempre algo de formalidad y cortesía; si usted
quiere, caballero, irá a disfrutar de su hospitalidad.
 Ya he hablado de Balseiro en la primera parte de
esta narración. Hallábase ahora encerrado en el piso
más alto de la cárcel, en un calabozo muy seguro, con
otros malhechores. Había sido condenado, en unión de
un Pepe Candelas, ladrón de no corta fama, por un
audacísimo robo cometido, en pleno día, nada menos
que en la persona de la modista de la reina, una
francesa, a quien ataron en una tienda, robándole
dinero y géneros por valor de cinco a seis mil duros.
Candelas había ya expiado su crimen en el patíbulo;
pero Balseiro, que era, en opinión común, el peor de los
dos bandidos, había logrado salvar la vida a fuerza de
dinero, un aliado con que su compañero no contaba; le
conmutaron la pena de muerte, a que fué sentenciado,
por la de veinte años de cadena en el presidio de
Málaga. Visité al héroe y conversé con él un rato a
través de la reja del calabozo. Me reconoció y me hizo
recordar la victoria que obtuve sobre él en la disputa
acerca de nuestros respectivos conocimientos en gitano
cerrado, en el que Sevilla, el torero, no tenía par.
Al decirle que sentía verle en tal situación, me
replicó que el asunto no tenía importancia, porque
dentro de seis semanas le llevarían al presidio, y una
vez allí, con ayuda de unas onzas bien distribuídas entre
sus guardianes, se escaparía cuando quisiera.
—Pero ¿adónde vas a ir?—le pregunté.
—¿No puedo irme a tierra de moros—replicó Balseiro
—, o con los ingleses al campo de Gibraltar, o, si lo
prefiero, no puedo volver a este foro y vivir como hasta
aquí, choring a los gachós? ¿Qué me cuesta
esconderme? Madrid es grande, y Balseiro tiene muchos
amigos, especialmente entre los lumias—añadió con
una sonrisa.
 Le hablé de su malhadado cómplice Candelas, y su
rostro tomó una expresión horrible.
—Supongo que estará en los infiernos—exclamó el
ladrón.
La amistad del inicuo nunca es de larga duración.
Los dos héroes regañaron, a lo que parece, en la cárcel,
acusándole Candelas al otro de haber procedido con
mala fe y haberse apropiado indebidamente, para su
disfrute personal, el corpus delicti en varios robos
cometidos en compañía.
No puedo resistir al deseo de contar las aventuras
ulteriores de Balseiro.
Poco después de mi salida de la cárcel, Balseiro, con
poca paciencia para esperar a que el presidio le
ofreciese la ocasión de recobrar la libertad, agujereó el
techo de la cárcel, y en compañía de otros penados se
fugó. Volvió al instante a sus primeros hábitos,
cometiendo muchos robos atrevidos dentro de Madrid y
en los alrededores. Voy a referir el último, al que puedo
llamar su crimen maestro, singular ejemplo de maldad.
Los robos callejeros y el escalo no le satisfacían, y
resolvió dar un gran golpe con el que esperaba ganar
dinero suficiente para irse a vivir con lujo y esplendor a
cualquier país extranjero.
Había cierto intendente de la Casa Real, llamado
Gabiria, vasco de nacimiento y dueño de inmensas
riquezas, que tenía dos hijos, dos guapos chicos de
doce a catorce años de edad, a quienes yo había visto a
menudo y hasta hablado con ellos en mis correrías por
la orilla del Manzanares, su paseo favorito. Los dos
muchachos estaban educándose, en aquel tiempo, en
cierto colegio de Madrid. Balseiro, conocedor del cariño
que su padre les tenía, determinó servirse de él en
provecho de su rapacidad. Trazó un plan, que consistía
ni más ni menos que en secuestrar a los chicos y no
devolverlos sino mediante un rescate enorme. El plan
fué ejecutado en parte: dos cómplices de Balseiro, bien
vestidos, llamaron a la puerta del colegio donde estaban
los chicos, y valiéndose de una carta falsificada, que
dieron como escrita por el padre, arrancaron al director
del colegio el permiso para llevarse a los chicos a pasar
un día de campo. A unas cinco leguas de Madrid,
Balseiro tenía una cueva, en un lugar solitario y agreste,
entre El Escorial y un pueblo llamado Torrelodones; allí
llevaron a los muchachos, donde quedaron bajo la
custodia de los dos cómplices; Balseiro permaneció en
Madrid con objeto de entrar en negociaciones con el
padre. Pero éste, hombre de notable resolución, en
lugar de acceder a las peticiones del bandido
formuladas por carta, adoptó sin perder tiempo medidas
muy enérgicas para recobrar sus hijos.
Envióse gente a pie y a caballo a recorrer la
comarca, y antes de una semana descubrieron a los
muchachos cerca de la cueva, abandonados por sus
guardianes, que cogieron miedo al enterarse de la
resolución con que los buscaban; no tardaron en
detenerlos, sin embargo, y los muchachos reconocieron
a sus secuestradores.
Balseiro comprendió que Madrid se ponía inhabitable
para él, y quiso escaparse, no sé si a la tierra del moro
o al Campo de Gibraltar; pero reconocido en un pueblo
cercano a Madrid, fué preso, y sin tardanza llevado a la
capital, donde a poco perdió la vida en el patíbulo con
sus dos cómplices; Gabiria y sus hijos presenciaron la
horrible escena a sus anchas, subidos en un carruaje.
 Tal fin tuvo Balseiro, de quien no hubiera hablado
tanto a no ser por lo del gitano cerrado. ¡Pobre
desventurado! Conquistó el género de inmortalidad a
que aspiran tantos ladrones españoles, mientras lucen
su nívea ropa blanca pavoneándose en el patio. El rapto
de los hijos de Gabiria le convirtió de golpe en ídolo de
toda la cofradía. Un ladrón famoso, con quien más
adelante estuve yo encarcelado en Sevilla, pronunció su
elogio en esta forma:
—Balseiro era un hombre muy cabal y muy buena
persona. Hacía cabeza de nuestro gremio, Don Jorge;
ya no volveremos a verle. ¡Lástima que no pudiera sacar
el parné y escaparse a tierra de moros, Don Jorge!
 CAPÍTULO XLI

María Díaz. — Reproches del clero. — Visita de Antonio.

— Antonio en funciones. — Una escena. —
Benedicto Mol. — Su peregrinación por España. —
Los cuatro Evangelios.

—S epamos—dije a María Díaz tres mañanas después

de mi encarcelamiento—. ¿Qué dice en Madrid la gente
a propósito de este suceso?
—No sé lo que la gente, en general, dirá;
probablemente no le importará esto gran cosa. La
verdad, son ya cosa tan corriente las prisiones, que el
público parece que las mira con indiferencia; pero los
curas andan muy revueltos, y confiesan la imprudencia
que han cometido al hacer que su amigo el corregidor le
prenda a usted.
—¿Cómo es eso? ¿Temen que castiguen a su amigo?
—No tal, señor—replicó María—Eso les importaría
poco, aunque el corregidor se la haya buscado buena
por servirlos; esa gente no tiene afectos, y no se les
daría un ardite que colgasen a todos sus amigos,
quedando ellos en salvo. Pero dicen que han procedido
de ligero al meterle a usted en la cárcel, porque al
hacer eso le han dado a usted ocasión de poner en
práctica un plan antiguo. «Ese individuo es un bribón—
dicen—. Se ha hecho amigo de los presos, y le han
enseñado su lengua, que ya hablaba casi tan bien como
si hubiera nacido en la cárcel. En cuanto le pongan en
libertad publicará un Evangelio para que lo lean los
ladrones, y será mucho más peligroso que el Evangelio
en gitano, porque los gitanos son pocos, pero los
ladrones...! ¡Ay de nosotros! ¡Todos vamos a ser
luteranizados! ¡Qué infamia, qué picardía! Todo esto ha
sido una treta suya. Siempre ha tenido ganas de ir a la
cárcel el bribonazo; en mal hora le hemos metido en
ella. España no estará segura hasta que le ahorquen;
hay que mandarle al quinto infierno, y allí tendrá tiempo
de traducir sus fatales Evangelios al lenguaje de los
demonios.»
—No le he dicho al alcaide arriba de tres palabras
acerca de la jerga de las cárceles.
—¿Tres palabras? Don Jorge, ¿qué no se puede
hacer con esas tres palabras? De poco le ha servido a
usted vivir entre nosotros si cree que necesitamos más
de tres palabras para armar un embrollo. Esas tres
palabras acerca del lenguaje de los ladrones bastan
para que por todo Madrid se diga que anda
entremezclado con ellos, que ha aprendido su lenguaje
y ha escrito un libro que va a trastornar a España, a
abrir a los ingleses las puertas de Cádiz, entregar a
Mendizábal toda la plata y las joyas de las iglesias, y a
Don Martín Lutero, el palacio arzobispal de Toledo.
Al caer la tarde de un día bastante melancólico, y
hallándome sentado en el aposento que el alcaide me
había destinado, oí un golpe en la puerta. «¿Quién
es?», pregunté. «C’est moi, mon maître», gritó una voz
muy conocida, y al instante entró Antonio Buchini,
vestido como la vez primera que le presenté al lector, es
decir, con un excelente sobretodo francés, ya un poco
ajado, chaqueta y pantalones, y en una mano, un
sombrero pequeñito, y en la otra, un bastón largo y
delgado.
—Bon jour, mon maître—dijo el griego. Echando una
mirada en torno, continuó:—Me alegro de verle a usted
bien instalado. Si no recuerdo mal, mon maître, en sitios
peores que éste hemos dormido durante nuestros viajes
por Galicia y Castilla.
—Tiene usted mucha razón, Antonio—repliqué—.
Aquí estoy muy cómodamente. Le agradezco la bondad
de haber venido a visitar a su antiguo amo, sobre todo
ahora, que está pasando trabajos. Supongo que por
venir aquí, no irá usted a enojar a su dueño actual; ya
debe de estar cerca la hora de comer. ¿Cómo ha
abandonado usted la cocina?
—¿A qué amo se refiere usted, mon maître?—
preguntó Antonio.
—¡De quién voy a hablar! Del Conde... por cuyo
servicio me dejó usted, tentado del ofrecimiento de
cuatro duros al mes sobre los que yo le daba.
—Su merced me hace recordar un asunto que ya
tenía olvidado por completo. Al presente no tengo otro
amo que usted, monsieur Georges, porque siempre le
considero a usted como tal, aunque no goce de la
felicidad de acompañarle.
—¿Entonces se marchó usted de casa del Conde a
los tres días de entrar, según costumbre?
—A las tres horas, mon maître—repuso Antonio—.
Pero yo le diré a usted en qué circunstancias. A poco de
separarme de usted, fuí a casa de monsieur le Comte;
entré en la cocina y miré en torno. No puedo decir que
me descontentase lo que vi: la cocina era cómoda y
espaciosa, todo estaba limpio y en orden; los criados
parecían amables y corteses; sin embargo, no sé cómo
fué, pero se apoderó de mí la idea de que la casa no me
convenía en modo alguno y que no estaría en ella
mucho tiempo; colgué de un clavo la mochila, y,
sentándome en la mesa de la cocina, empecé a cantar
una canción griega, como hago siempre que estoy
disgustado. Rodeáronme los criados, haciéndome
preguntas; pero yo no les contesté, y continué cantando
hasta que se acercó la hora de preparar la comida;
entonces salté al suelo de pronto y los eché de la cocina
a todos, diciéndoles que nada tenían que hacer allí en
tal ocasión. Al momento entré en funciones. Hice un
esfuerzo, mon maître, y me puse a preparar una comida
que me hubiese hecho honor; había convidados aquel
día y determiné, por tanto, demostrar a mi amo que la
capacidad de su cocinero griego era insuperable. Eh
bien, mon maître, todo marchaba bastante bien, y casi
me encontraba ya a gusto en mi nuevo empleo, cuando
se precipitó en la cocina le fils de la maison, mi
señorito, un chiquillo de unos trece años, bastante feo.
Llevaba en la mano una rebanada de pan, y, después de
un breve reconocimiento, la sepultó en una cacerola
donde se guisaban unas perdices. Ya sabe usted, mon
maître, que soy muy delicado en ciertas cuestiones,
porque no soy español, sino griego, y tengo principios
de honor. Sin vacilar un momento, cogí a mi señorito
por los hombros, y empujándole hacia la puerta, le
despedí como merecía. Con gritos clamorosos subió
corriendo al piso alto. Yo continué en mi trabajo, pero
no habían pasado tres minutos cuando oí un pavoroso
estrépito en lo alto de la escalera, on faisoit un horrible
tintamarre, y de vez en cuando oía juramentos y
maldiciones. Al instante la puerta se abrió con violencia,
y en impetuosa carrera echaron escaleras abajo el
Conde, mi señor, su mujer, mi señorito, seguidos de una
regular bandada de mujeres y de filles de chambre. A
todos los llevaba gran delantera el Conde, mi señor, con
una espada desnuda en la mano y gritando: «¿Dónde
está el malvado que ha deshonrado a mi hijo? ¿Dónde
está, que lo mato ahora mismo?» Yo no sé cómo
ocurrió, mon maître, pero, cabalmente, en aquel
momento volqué una gran fuente de garbanzos
destinados a la puchera del día siguiente. Estaban
crudos, y tan duros como piedras; los derramé por el
suelo, y la mayor parte de ellos fué a parar junto a la
entrada. Eh bien, mon maître, un instante después
entró el Conde de un brinco, echando chispas por los
ojos, y con una espada en la mano, como ya he dicho.
«Tenez, gueux enragé», me gritó, tirándome una
furiosa estocada; pero no había acabado de decir esas
palabras, cuando resbaló, y cayó hacia adelante todo lo
largo que era, y la espada se le escapó de la mano
comme une flêche. ¡Si hubiese usted oído el alboroto
que se armó! Hubo una confusión terrible: el Conde
yacía en el suelo, al parecer, aturdido por el golpe. Yo
no hice caso, y continué trabajando con afán. Al fin le
levantaron, y con sus cuidados recobró el sentido;
estaba muy pálido y agitado. Pidió la espada; todas las
miradas se clavaron en mí, y adiviné que se preparaba
un ataque general. De súbito, retiré del fuego una gran
casserole, donde se freían unos huevos, y la mantuve a
la distancia que permitía la longitud del brazo,
examinándola con afectada atención, mientras avanzaba
el pie derecho y echaba atrás el izquierdo cuanto podía.
Todos se estuvieron quietos, figurándose que iba a
hacer una operación importante, y así fué, en efecto,
porque adelanté de pronto la pierna izquierda, y con un
rápido coup de pied, lancé la casserole y su contenido
por encima de mi cabeza con tal fuerza, que fueron
volando a estamparse en una pared bastante detrás de
mí. Esto lo hice para significar que el trato quedaba roto
y que sacudía el polvo de mis zapatos; arrojé sobre el
Conde la mirada peculiar de los cocineros scirotas
cuando se sienten insultados, y, dilatando mi boca por
ambos lados hasta cerca de las orejas, descolgué la
mochila y me fuí, cantando al marcharme la canción del
antiguo Demos, quien, moribundo, pedía la comida y
agua para lavarse las manos:
Ὁ ἥλιος ἐβασίλευε, κι᾽ ὁ Δῆμος διατάζει.
Σύρτε, παιδιά μου, ᾽σ τὸ νερὸν ψωμὶ νὰ φάτ᾽ ἀπόψε.

De esta manera, mon maître, salí de casa del Conde.

Yo.—¡Excelente manera de portarse! Por confesión
propia, veo que su conducta no ha podido ser peor. Si
no fuera por las muchas pruebas de valor y fidelidad
que me dió usted estando a mi servicio, desde este
momento no volveríamos a vernos más.
Antonio.—Mais qu’est ce que vous voudriez, mon
maître? ¿No soy griego, y hombre de honor y muy
susceptible? ¿Quiere usted que los cocineros de Scira y
de Stambul se sometan en España a que los insulten los
hijos de los condes, precipitándose en el templo con
rebanadas de pan? Non, non, mon maître, usted es
demasiado noble y, sobre todo, demasiado justo para
pedir eso. Pero hablemos de otra cosa. Mon maître, no
he venido solo: en el corredor espera una persona que
ansía verle a usted.
Yo.—¿Quién es?
Antonio.—Uno a quien ya se ha encontrado usted,
mon maître, en sitios muy extraños y diversos.
Yo.—Pero ¿de quién se trata?
 Antonio.—De uno a quien le aguarda un fin
desusado, «porque así está escrito». El suizo más
extraordinario que hay, el de Santiago: der Schatz
Gräber.
Yo.—¿Benedicto Mol?
—Yaw, mein lieber Herr—dijo Benedicto, abriendo
del todo la puerta, que estaba entornada—. Soy yo. Me
he encontrado en la calle a Herr Anton, y al oír que
estaba usted aquí, he venido a visitarle.
Yo.—Pero ¿qué rareza es ésta, y cómo es que le veo
a usted otra vez en Madrid? Yo creía que ya estaba
usted en su país.
Benedicto.—No tema, lieber Herr; allá he de volver a
su debido tiempo, pero no a pie, sino en coche de
mulas. El Schatz se está todavía en su escondite,
esperando que lo desentierren; ahora tengo mejores
esperanzas que nunca; muchos amigos, mucho dinero.
¿Ha reparado usted cómo voy vestido, lieber Herr?
En efecto, llevaba ropas mucho mejores que nunca.
La chaqueta y los pantalones, de crudillo, eran casi
nuevos. Tocábase aún con un sombrero andaluz, de
forma cónica, pero no viejo ni raído, sino nuevo y
lustroso, y de inmensa altura. En lugar del tosco palo
que llevaba en Santiago y en Oviedo, traía ahora una
recia caña de bambú, rematada por una disforme
cabeza de oso o de león, prolijamente tallada en peltre.
—Parece usted un buscador de tesoros al volver de
una expedición fructífera—exclamé.
—Más bien parece—interrumpió Antonio—uno que
ha dejado de trabajar por cuenta propia y busca tesoros
a costa ajena.
 Pregunté detalladamente al suizo por sus aventuras
desde que le vi por última vez en Oviedo, donde le dejé
para continuar mi viaje a Santander. De sus respuestas
colegí que me había seguido hasta este último punto,
pero invirtiendo mucho tiempo en el camino, debilitado
por el hambre y las privaciones. En Santander me
perdió el rastro. Ya se le había agotado el pequeño
socorro que yo le dí. Pensó entonces irse a Francia,
pero no se atrevió a aventurarse en las provincias
Vascongadas, donde ardía la guerra, para no caer en
manos de los carlistas, que hubieran podido fusilarle por
espía. Como nadie le socorría en Santander, se fué
pidiendo limosna por los caminos, hasta que se
encontró en Aragón, no podía decir exactamente dónde.
«Mis calamidades eran tantas—dijo Benedicto—que
estuve a punto de perder el juicio. ¡Oh, qué horror,
vagar por los agrestes montes y las vastas planicies de
España, sin dinero y sin esperanza! Algunas veces,
encontrándome entre peñas y barrancos, quizás sin
haber probado alimento desde la salida hasta la puesta
del sol, me enfurecía. Entonces levantaba el palo hacia
el cielo, y, blandiéndolo, gritaba: Lieber Herr Gott, ach
lieber Herr Gott, ahora más que nunca necesito tu
ayuda; si tardas en socorrerme estoy perdido;
¡ayúdame ahora, ahora! Y una vez, cuando deliraba de
ese modo, me pareció oír una voz—más, estoy seguro
de haberla oído—que sonaba en la cavidad de una
peña, muy clara y muy fuerte, gritando: «Der Schatz,
der Schatz, no hay que desenterrarlo todavía; a Madrid,
a Madrid. El camino del Schatz pasa por Madrid.» De
nuevo la idea del Schatz se apoderó de mi ánimo;
reflexioné en lo feliz que sería si pudiese desenterrarlo.
¡No más mendigar, no más errar por hórridas montañas
y desiertos! Blandí el palo, y noté, con sorpresa, que mi
cuerpo y mis miembros se reanimaban con nuevas
energías; anduve a buen paso, y no tardé en salir al
camino real; mendigué, y proseguí como mejor pude
hasta llegar a Madrid.
—¿Y qué le ha sucedido después de llegar a Madrid?
—pregunté—. ¿Ha encontrado usted el tesoro en las
calles?
De pronto, Benedicto se volvió reservado y taciturno,
cosa que me sorprendió en extremo, porque hasta
entonces se había mostrado siempre muy comunicativo
en lo tocante a sus cuentas y proyectos. Por lo que
pude sacar de sus medias palabras e insinuaciones,
parecía que al llegar a Madrid cayó en manos de ciertas
personas que le trataron con bondad, proveyéndole de
dinero y ropa; no por puro desinterés, sino con los ojos
puestos en el tesoro. «Esperan mucho de mí—dijo el
suizo—. Después de todo, acaso hubiera sido más
ventajoso sacar el tesoro sin su ayuda, con tal que
hubiese sido posible.» No sabía o no quiso decirme
quiénes eran sus nuevos amigos, salvo que tenían
muchísima influencia. Dijo algo acerca de la Reina
Cristina, y de un juramento que había prestado ante un
obispo, sobre un crucifijo y los cuatro Evangelien. Pensé
que había perdido la cabeza, y dejé de preguntarle. En
el momento de marcharse, me dijo: «Lieber Herr,
dispénseme usted si no le he hablado con entera
franqueza, debiéndole tanto como le debo, pero no me
atrevo; ahora no me pertenezco. Además, siempre es
de mal agüero hablar una palabra acerca de un tesoro
antes de tenerlo en nuestro poder. Una vez, en mi país
hubo un hombre que cavó en el suelo hasta descubrir
un caldero de cobre que contenía un Schatz. Al cogerlo
por el asa, no hizo más que exclamar, en su
entusiasmo: “¡Ya lo tengo!”, y eso bastó: desprendióse
la caldera y se hundió, quedándose el hombre con el
asa en la mano: eso fué cuanto ganó con tantos
trabajos. Adiós, lieber Herr; dentro de poco me
mandarán a Santiago para desenterrar el Schatz, pero
vendré a verle a usted antes de marcharme. ¡Adiós!»
 CAPÍTULO XLII

Salida de la cárcel. — Las excusas. — El corazón

humano. — La vuelta del griego. — La Iglesia
romana. — La luz de la Escritura. — El arzobispo de
Toledo. — Una entrevista. — Piedras preciosas. —
Una resolución. — El lenguaje extranjero. —
Despedida de Benedicto. — La caza del tesoro en
Compostela. — Realidad y ficción.

U nas tressemanas estuve en la cárcel de Madrid, y, al

cabo de ese tiempo la dejé. Si yo hubiese sido
orgulloso, o abrigado algún rencor contra el partido que
me encarceló, el modo como me devolvían la libertad
hubiera halagado grandemente esas malas pasiones. El
Gobierno, en un documento transmitido a sir Jorge,
reconoció que me habían detenido sin razón bastante, y
que ninguna tacha quedaba sobre mí de resultas de la
prisión; se encargaba al propio tiempo de pagar todos
los gastos que la tramitación del asunto me originó.
Además, se mostró dispuesto a dejar cesante al
individuo por cuyos informes me detuvieron, es decir, el
corchete que me visitó en mi hospedaje de la calle de
Santiago y se comportó del modo descrito en uno de los
anteriores capítulos. Rehusé, empero, aprovecharme de
la condescendencia del Gobierno, más que nada porque
me dijeron que el individuo de marras tenía mujer e
hijos, y si le dejaban cesante, se quedarían en la
miseria. Consideré, además, que en cuanto hizo y dijo
se limitó probablemente a obedecer órdenes secretas;
le perdoné, pues, sin reservas, y si en el momento
presente no conserva su plaza, la culpa, ciertamente, no
es mía.
También rehusé aceptar indemnización por mis
gastos, que fueron de importancia. Es probable que
muchas personas en mi caso hubiesen procedido de
muy diferente modo en este punto, y me guardo de
afirmar que en ello anduviese yo del todo discreto o
acertado. Pero me repugnaba recibir dinero de una
gente como la que componía el Gobierno de España,
gente a quien, lo confieso, despreciaba yo cordialmente,
y no quería darle motivo para decir que el inglés a quien
habían apresado injustamente y sin proceso, accedía a
recibir dinero de sus manos. En una palabra, confieso
mi debilidad: deseaba yo que continuasen siendo
deudores míos, y estaba seguro de que no opondrían la
más leve objeción a continuar siéndolo; se guardaron su
dinero y probablemente se rieron para su capote de mi
falta de sentido común.
La mayor pérdida que me ocasionó el
encarcelamiento, y por la que no podía ofrecerse ni
recibirse indemnización, fué la muerte de mi afectuoso y
fiel Francisco, el vascongado, que por acompañarme
durante todo el tiempo que duró mi prisión, cogió el
tifus o fiebre carcelaria, que entonces hacía estragos en
la cárcel de la Corte, y murió a los pocos días de mi
liberación. Murió ya entrada la noche. A la mañana
siguiente estaba yo en la cama reflexionando sobre esta
pérdida, y me preguntaba de qué nación sería mi
servidor futuro, cuando oí un ruido al parecer causado
por una persona ocupada en limpiar vigorosamente
zapatos o botas, y a intervalos una voz extraña y
discordante que cantaba trozos de una canción en una
lengua desconocida; no sabiendo lo que aquello podría
ser, toqué la campanilla.
—¿Ha llamado usted, mon maître?—dijo Antonio
asomándose a la puerta con uno de los brazos
profundamente sepultado en una bota.
—Sí, por cierto—contesté—; pero no me podía
imaginar que fuese usted quien respondiera a la
llamada.
—Mais pourquoi non, mon maître?—exclamó Antonio
—. ¿Quién va a servirle a usted ahora sino yo? N’est pas
que le sieur François est mort? En cuanto lo supe, me
dije: voy a volver a mi puesto chez mon maître,
monsieur Georges.
—Supongo que estará usted sin colocación, y por
eso ha venido.
—Au contraire, mon maître—replicó el griego.
Acababa de ajustarme en casa del duque de Frías,
donde me daban al mes diez duros más que su merced;
pero al saber que se había usted quedado sin criado, fuí
sin pérdida de tiempo a decir al duque, aunque ya
estaba muy entrada la noche, que no me convenía
servirle; y aquí estoy.
—Pues de esa manera, no le admito—dije yo—.
Vuelva a casa del duque, preséntele sus excusas por lo
que ha hecho, y solicite su cese en debida forma;
entonces, si su gracia desea prescindir de usted, caso
bastante probable, le admitiré con mucho gusto a mi
servicio.
 Después de sufrir una prisión cuya injusticia
reconocían mis propios enemigos, era razonable esperar
de sus manos un trato más liberal que el que hasta allí
me habían dispensado. Mi única ambición era por
entonces conseguir tolerancia para la venta del
Evangelio en aquel infortunado y perturbado reino; para
lograr ese fin no sólo hubiera consentido en sufrir, uno
tras otro, veinte encarcelamientos como el pasado, sino
que hubiera sacrificado gustoso la vida misma. Pronto
advertí, sin embargo, que probablemente no iba a ganar
nada con mi encarcelación; al contrario, desde que se
concluyó el asunto, fuí objeto de la aversión personal
del Gobierno, lo que tal vez no sucedía antes; las
concesiones que se vieron obligados a hacer para evitar
una ruptura con Inglaterra humillaron su orgullo y
vanidad. Mostráronse dispuestos a saciar su aversión,
contrariando mis planes todo lo posible. Tuve una
entrevista con Ofalia acerca del asunto que embargaba
mi ánimo; le encontré desabrido y áspero. «Lo que más
le conviene a usted es permanecer tranquilo—me dijo—.
¡Cuidado! Ya ha puesto usted una vez toda la corte en
confusión; cuidado, repito. Otra vez puede que no se
escape usted tan fácilmente.»
—Quizás no—repliqué—y quizás ni lo deseo siquiera;
es cosa agradable padecer por la causa del Evangelio.
Ahora me tomaré la libertad de preguntar si, en el caso
de ponerme a propagar la Palabra de Dios, me lo
impedirán.
—Naturalmente—exclamó Ofalia—; la Iglesia lo
prohibe.
—Pues, con todo, voy a intentarlo—exclamé.
—¿Sabe usted lo que dice?—preguntó Ofalia,
arqueando las cejas y abriendo la boca.
 —Sí, continué—; voy a hacer la prueba en todos los
pueblos de España donde me sea posible entrar.
Durante mi permanencia en España, la oposición
más recia que encontré fué la del clero; por instigación
suya el Gobierno adoptaba las medidas convenientes
para impedir la amplia difusión del libro sagrado por el
país. No interrumpiré el curso de mi narración con
reflexiones acerca de la situación de una Iglesia que, si
bien pretende fundarse en la Escritura, arrebataría la luz
de la Escritura a toda la Humanidad, si pudiese. Pero
Roma sabe perfectamente que no es una Iglesia
cristiana, y como no tiene deseo de serlo, obra
cuerdamente quitando a sus secuaces de delante de los
ojos las páginas que podrían revelarles las verdades del
Cristianismo. Sus agentes y validos en España
esforzábanse cuanto podían por anular mis humildes
trabajos y difamar la obra que yo andaba esparciendo.
Todo el clero ignorante y fanático (la gran mayoría) era
opuesto a ella, y cuantos ansiaban estar a bien con la
corte de Roma vociferaban su oposición. Había, empero,
una parte del clero, pequeña a la verdad, bien dispuesta
en favor de la circulación del Evangelio, aunque en
modo alguno inclinada a hacer el menor sacrificio
individual por tal fin; éstos eran los que profesaban el
liberalismo, que se supone implica una disposición a
adoptar cuantas reformas, así en lo civil como en lo
eclesiástico, parezcan conducentes al bien del país. No
pocos clérigos españoles eran partidarios de ese
principio, o al menos se declaraban tales; algunos, por
conveniencia propia sin duda, con la esperanza de
aprovechar el espíritu de los tiempos para su medro
personal; otros, hay que esperarlo, por convicción, por
puro amor a las ideas. Entre éstos se encontraban, por
la época a que me refiero, varios obispos. Pero es digno
de nota que ninguno de ellos debía su puesto al Papa,
que los desautorizaba, sino a la Reina Gobernadora,
cabeza visible del liberalismo en España. No es de
extrañar, por tanto, que hombres colocados en tales
circunstancias se sintiesen dispuestos a apoyar
cualquier medida o plan favorables al progreso del
liberalismo, más bien que a contrariarlos; y no hay duda
que la circulación de la Escritura era una medida de ese
género. Con todo, su buena voluntad, suponiendo que
la tuvieran, fué para mí poco valiosa, porque nunca
dieron un paso decisivo ni alzaron sus voces para
denunciar de modo positiva y resuelto la conducta de
quienes pretendían privar al mundo de la luz de la
Escritura. En cierta ocasión creí que iba a conseguir, por
su medio, algo importante para la causa del Evangelio
en España; pero me desengañé pronto, y me convencí
de que descansar en lo que quisieran hacer era tanto
como apoyar la mano en una caña, que, sin
sostenerme, me desgarraría la carne. Algunos de ellos
me enviaron mensajes expresando la estimación en que
me tenían y asegurándome cuán cara a su corazón era
la causa del Evangelio. Recibí incluso un aviso
insinuándome que mi visita no sería desagradable al
arzobispo de Toledo, Primado de España.
Poco puedo decir de este personaje, cuya historia
desconozco por completo. A la muerte de Fernando era,
creo yo, obispo de Mallorca, pequeña e insignificante
sede, de muy pobres rentas, que quizás cambió gustoso
por otra más rica. Es probable, sin embargo, que de
mostrarse fiel servidor del Papa, y, por ende, partidario
de los legitimistas, hubiera ocupado hasta el día de su
muerte la silla episcopal de Mallorca; pero pasaba por
liberal, y la Reina Gobernadora tuvo a bien concederle la
dignidad de arzobispo de Toledo, haciéndole así cabeza
de la Iglesia en España. Cierto que el Papa se negó a
ratificar la designación, razón por la que todos los
buenos católicos estaban obligados a seguir
considerándole como obispo de Mallorca y no como
Primado de España. Pero el obispo cobraba las rentas
de la sede toledana, débil sombra de lo que fueron
antaño, pero muy importantes aún, y vivía en el palacio
del Primado, en Madrid, de suerte que si no era
arzobispo de jure era lo que para muchos valía más:
arzobispo de facto.
Sabedor de la amistad personal del arzobispo con
Ofalia, quien, según decían, le consideraba mucho,
resolví hacerle una visita, y así una mañana me
encaminé al palacio en que vivía. Sin dificultad obtuve
audiencia: un lacayo, asturiano a lo que creo, a quien
hallé sentado en un banco de piedra del portal, me
condujo a su presencia. Cuando entré, el arzobispo
estaba solo, sentado detrás de una mesa, en un vasto
aposento, especie de sala de estrados. Vestía con
sencillez: sotana negra y birrete de seda; pero en un
dedo llevaba una amatista soberbia, resplandeciente, de
brillo deslumbrador. Se incorporó un momento, al
acercarme, y con la mano me indicó una silla. Podía
tener sesenta años; era muy alto, pero se encorvaba
bastante, por debilidad sin duda; y la tez pálida de sus
facciones demacradas denotaba su mala salud. Cuando
de nuevo se sentó inclinó la cabeza, como si
contemplase la mesa que tenía delante.
—Supongo que V.E. sabrá quién soy—dije al cabo,
rompiendo el silencio.
El arzobispo inclinó la cabeza hacia el hombro
izquierdo, con expresión algo equívoca, pero no dijo
nada.
—Yo soy el que los Manolos de Madrid llaman Don
Jorgito el Inglés. Acabo de salir de la cárcel, donde me
encerraron por propagar el Evangelio del Señor en este
reino de España.
El arzobispo repitió el mismo movimiento equívoco
de la cabeza, pero aún no dijo nada.
—He sabido que V.E. deseaba verme, y por esa
razón he venido a hacerle esta visita.
—Yo no le he llamado a usted—dijo el arzobispo,
alzando de súbito la cabeza, y con ojos de espanto.
—Quizás no; pero me habían dado a entender que
mi presencia sería grata; como al parecer no es así, me
iré.
—Puesto que ha venido usted, me alegro mucho de
verle.
—Y yo celebro mucho oírle—dije yo, volviendo a
sentarme—. Ya que estoy aquí, podemos hablar de un
asunto de la mayor importancia: la difusión de la
Escritura. ¿Conoce V.E. algún medio para alcanzar un fin
tan deseable?
—No—dijo el arzobispo débilmente.
—¿No cree V.E. que el conocimiento de la Escritura
produciría inestimables beneficios a estos reinos?
—No lo sé.
—¿Hay probabilidades de convencer al Gobierno
para que consienta su circulación?
—¿Cómo voy a saberlo?—y el arzobispo se me
quedó mirando a la cara.
Yo también le miré a él; había en su rostro tal
expresión de desvalimiento, que casi era chochez.
«¡Válgame Dios!—pensé—. ¿A quién he venido yo a
contar estas cosas? ¡Pobre hombre! No sirves para
representar el papel de Martín Lutero, y en España
menos que en otra parte. Me maravilla que tus amigos
te hayan nombrado arzobispo de Toledo. Quizás
pensaron que no harías provecho ni daño, y te
escogieron, como escogen a veces en mi país a los
primados, en razón de tu incapacidad. No pareces muy
contento en este empleo, ni tu sitial debe de ser muy
cómodo. Más a gusto estabas cuando eras el pobre
obispo de Mallorca; entonces podías saborear la
puchera sin miedo de que te la sazonaran con
sublimado. No temías entonces que te ahogaran en el
lecho. La siesta es cosa agradable, cuando no está uno
expuesto a verla interrumpida por un súbito espanto.
Me sorprenderá si no estás ya envenenado»—continué
casi en voz alta, según estaba mirándole al semblante,
que a mi parecer se cubría de palidez mortal.
—¿Qué decía usted, don Jorge?—preguntó el
arzobispo.
—Que V.E. lleva un brillante magnífico—dije yo.
—¿Le gustan a usted los brillantes, don Jorge?—dijo
el arzobispo, cuyas facciones se animaron—. ¡Vaya!
¡También a mí! ¡Son muy bonitos! ¿Entiende usted de
brillantes?
—Sí entiendo—respondí—, y no he visto nunca otro
mejor que ése, salvo uno, perteneciente a un conocido
mío, un khan de Tartaria. Pero no lo llevaba en el dedo;
poníaselo al caballo en el frontal, donde brillaba como
una estrella. Llamábalo Daoud Scharr, que significa «luz
de guerra».
 —¡Vaya!—dijo el arzobispo—. ¡Qué curioso! Me
alegro de que le gusten a usted los brillantes, don
Jorge. Al hablar de caballos me ha hecho usted recordar
que le he visto con frecuencia a caballo. ¡Vaya! Qué
modo de montar. Es peligroso encontrársele a usted en
el camino.
—¿V.E. es aficionado a la equitación?
—De ninguna manera, don Jorge. No me gustan los
caballos. En la Iglesia no es costumbre montar a
caballo; preferimos las mulas: son animales más
tranquilos. Los caballos me dan miedo: ¡cocean de un
modo!
—La coz del caballo mata—dije yo—si da en un sitio
vital. Pero no opino como V.E. acerca de las mulas; un
buen jinete puede sostenerse a caballo, por resabiado
que el animal esté; pero las mulas, ¡vaya!, cuando una
mula falsa tira por detrás, no creo que ni el propio
Padre de la Iglesia se sostenga en la silla ni un
momento, por muy buen bocado que lleve.
Al marcharme, le dije:—¿Qué puedo esperar acerca
del Evangelio?
—No sé—dijo el arzobispo inclinando de nuevo la
cabeza hacia el hombro derecho, mientras sus facciones
reasumían la expresión de vaciedad.
Así terminó mi entrevista con el arzobispo de Toledo.
—Me parece—dije a María Díaz al volver a casa—,
me parece, Mariquita mía, que si el Evangelio, para ser
tolerado en España, ha de esperar a que los obispos y
arzobispos liberales acudan resueltamente en su ayuda,
va a tener que aguardar mucho tiempo.
 —Soy del mismo parecer, señor—respondió María—.
¡Bonito sería tener que esperar a que esa gente haga
un esfuerzo en favor de usted! ¡Ca! Risa me da
pensarlo. ¿Cómo ha tenido usted la candidez de
figurarse que les importa algo el Evangelio? ¡Vaya!, son
verdaderos curas; en los ofrecimientos que le han hecho
a usted sólo les movía su propio interés. El Santo Padre
no quiere reconocerlos, y les gustaría asustarle un poco
para obligarle a transigir; pero como los reconociera, ya
vería usted luego si le admitían en sus palacios o tenían
algún trato con usted. «¡Fuera ese prójimo!—dirían—.
¡Vaya! ¿No es luterano? ¿No es enemigo de la Iglesia?
¡A la horca, a la horca!» Conozco a esa familia mejor
que usted, don Jorge.
—Es inútil aguardar más—dije yo—. Pero en Madrid
nada puedo hacer. No se puede vender la obra en el
despacho, y acabo de saber que todos los ejemplares
dejados para la venta en las librerías de las diversas
poblaciones que he visitado los ha secuestrado el
Gobierno. Mi decisión está tomada: montaré en mis
caballos, que relinchan en la cuadra, y me iré a recorrer
en persona los pueblos y llanuras de la polvorienta
España. Al campo, al campo. «Camina, avanza
prósperamente y reina por medio de la verdad y de la
mansedumbre y de la justicia; tu diestra te conducirá a
cosas maravillosas.» Caminaré, pues, María.
—No puede hacer su merced cosa mejor, y
permítame ahora decirle que, por cada libro que pudiera
usted vender en un despacho en la ciudad, venderá
usted ciento en los pueblos con tal de darlos baratos,
porque en el campo hay poco dinero. ¡Vaya! ¿Sabré yo
lo que digo? ¿No soy también de pueblo, villana de la
Sagra? A caballo, pues; los caballos no hacen más que
relinchar en la cuadra, como usted dice, y casi podía
haber añadido que el señor Antonio relincha en la casa.
Dice que no tiene nada que hacer, motivo por el que
está otra vez disgustado e inquieto. Todo lo encuentra
mal, a mí en primer término. Esta mañana le saludé, y,
en lugar de contestarme, torció la boca de un modo
nunca visto en tierras de España.
—Se me ocurre una idea—dije yo—. Ha mentado
usted la Sagra ¿Por qué no comenzar mis trabajos por
los pueblos de esa comarca?
—Muy bien pensado—replicó María—. La recolección
termina ahora por allí, y encontrará usted a la gente
relativamente desocupada, con vagar para acompañarle
a usted y oírle. Si quiere seguir mi consejo, debe usted
establecerse en Villaseca en la casa que fué de mis
padres, donde al presente vive mi señor marido. Vaya
usted a Villaseca lo primero, y desde allí puede usted
emprender excursiones con el señor Antonio. Quizás mi
marido les acompañe; si es así, les servirá de mucho. La
gente en Villaseca es amable y cortés; cuando se
dirigen a un forastero le hablan a gritos y en gallego.
—¡En gallego!—exclamé.
—Todos saben unas cuantas palabras de gallego
aprendidas de los que bajan todos los años a segar, y
como el gallego es la única lengua extraña que
conocen, la emplean por cortesía al dirigirse a un
extranjero. ¡Vaya! No es mal pueblo Villaseca, ni es
mala gente; la única persona de mala condición que allí
hay es el reverendo señor cura.
No fueron largos los preparativos de mi empresa.
Envié por delante con un arriero un buen repuesto de
Testamentos, y yo salí al siguiente día. Pero antes de
marcharme recibí la visita de Benedicto Mol.
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