M.I.

1144
*Rev. B
ELECTRO-MOTIVE

AINTENANCE
INSTRUCTION

AIR COMPRESSOR MODELS WBO AND WBG

This Maintenance Instruction covers the WBO and The WBO compressor has two low pressure and one
WBG air compressors used on locomotives shipped high pressure cylinders and the WBG compressor
since January I. 1969 an<l provides instructions for has four low pressure and two high pressure
upgrading older versions of these two models. It cylinders. The low pressure cylinders are set at an
DOES NOT SUPERSEDE M.I. 1110 Rev. A which angle to the venical high pressure cylinder position.
covers compressor Models WXO, WXE, WXG, The pistons of the high and low pressure cylinders
ABO, ADJ, and ADX. are all driven by a common crankshaft.

DESCRIPTION Before it enters the compressor the air is cleaned by

passage through a dry-type air filter. On single filter
The WBO and WHG model air compressors, Fig. I, units the filter is mounted on the air inlet manifold.
arc water cooled, two stage air compressors. Each On dual filter units the filters arc mounted directly
compressor has its own oil pump and pressure onto each of the two low pressure cylinder heads.
lubricating system. Both models are equipped with a
deep sump oil pan in domestic applications. Export Air at atmospheric pressure is drawn in through the
units are equipped with a shallow sump oil pan. filter and intake valve into the low pressure

21216

WBO Fig.1 - Air Compressor WBG

*This bulletin is revised and supersedes previous issues of this number.

DE-L June 1983

M.L 1144

cylinders during the downward stroke of the piston. air to the unloader assembly, cutting out the
As the air is compressed on the upward stroke, the compressor action by holding the intake valve open.
inta kc valve is closed and the air at higher pressure is When reservoir pressure falls. the air operating the
forced through the discharge valve into the unloader is cut off, the intake valve is released, and
intercooler. Air leaves the intercooler, entering the the compressor resumes normal pumping.
high pressure cylinder through its intake valve. As
the high pressure piston moves upward, it compresses CRANKCASE BREATHER
the air to a higher pressure, forcing it out through
the discharge valve and connecting piping to the WBO compressors are equipped with a crankcase
mam air reservoir. hreather which permits a partial vacuum in the
compressor crankcase. To accomplish this, the
The inte rcooler contains passages for engine cooling breather acts as a check valve. When pressure builds
water and for air from the low pressure cylinders. It up in the crankcase as the pistons move down, the
acts to remove heat from the compressed air, breather valve opens. As the pistons start up, the
making it more dense, and thereby improving the breather valve closes, preventing the admission of
efficiency of the high pressure cylinder(s). fhe basic air into the crankcase.
intercooler has one water inlet and one water outlet, On springbacked valves there should be only a slight
but some intercoolers (two-pass) have one water tension in the spring. Excess tension will cause
inlet and two outlets to obtain parallel flows and abnormal pulsation at the breather as the pistons
more efficient cooling of the air. A two-pass move up and down. nullifying the purpose of the
intercooler is required for operating speeds of breather.
950 RPM or greater. Air flow is the same through
each type of intercooler. The breather. Figs. 2 & 3, is connected to the
compressor air intake manifold or to the filter. This
Since the compressor is driven by the engine, it is prevents the escape of vapors into the air around the
running whenever the engine is running. although compressor.
not continuously pumping air.
The breather should be cleaned periodically with
When main reservoir air reaches the recommended petroleum solvent and blown dry with compressed
pressure, the compressor governor control admits air.

SPRING-TYPE DIAPHRAGM-TYPE
27825

Fig.2 - Crankcase Breathers Applied To Earlier Units

-2-
 M.I. 1144

GEAR-TYPE OIL PUMP

The oil pump drive shaft is driven by a mating
helical gear that is shrunk on the crankshaft. Oil
under pressure is fed to the relief valve block and
returned by drilled passages in the crankcase to the
oil introducing ring that is housed in the small
bearing end plate. A drilled opening in the crankshaft
lines up with a circumferential groove in the oil
introducing ring LD. to feed oil to the drilled
passages in the crankshaft.

The lube oil filter provided with compressors that

are equipped with gear-type pumps is a spin-on, full
flow design with a built-in relief valve.

Units equipped with plunger-type pumps may be

REED-TYPE converted to gear-type by the procedure detailed in
27826
M.I. 9621.
Fig.3 - Basic Crankcase Breather
LUBRICATION REQUIREMENTS
It is important that the compressor crankcase oil be
LUBRICATING SYSTEM changed at intervals given in the applicable
The lubricating system is shown in Fig. 4. The Scheduled Maintenance Program. After draining
crankshaft is rifle drilled for passage of oil to the the oil, clean the inside of the crankcase by flushing
connecting rod bearings. Oil under pressure from with petroleum solvent and wipe clean with lint-
the lubricating oil pump flows through the drilled free, bound-edge towels. For compressor lubricating
passages of the crankshaft. The piston pin bearing oil specifications refer to the applicable Locomotive
and crankshaft main bearings are lubricated either Service Manual. For crankcase oil capacity, refer to
by the oil mist from the connecting rod oil throw-off the Service Data pages of this Maintenance
or by the flow of oil under pressure through rifle Instruction.
drilled connecting rods. The latter system is Oil level can be determined at any time, with the
required for idling speeds of 200 RPM or less. The compressor running or stopped. When the basic
drilled rod system requires a gear-type oil pump. float gauge is applied to the compressor, the gauge
needle must be kept in the green "RUN" area. When
the compressor is equipped with a dipstick-type oil
A block mounted on the side of the crankcase level gauge, oil should be added as indicated by the
houses a valve, Fig. 5, that is used to control oil dipstick reading. To take an oil level reading from a
pressure. This valve provides for correct minimum dipstick, first remove it, wipe it clean, and reinsert it,
oil pressure at idling speed and ensures adequate oil making certain that it is fully seated. Then remove
pressure at all speeds. the dipstick and make the reading. A low oil
protection sytem is available and is detailed in
CAUTION Maintenance Instruction 9638.
Do not put a locomotive into service with a
pressure gauge at the test opening. Failure of Oil pressure should be checked periodically to
the gauge can bring about serious compressor ensure that the pump and associated parts are
and engine damage. functioning properly. With engine at 315 RPM and
oil temperature at 60° C ( 140° F) oil pressure should
be l03 kPa (15 psi) minimum on new compressors
PLUNGER-TYPE OIL PUMP and 48 kPa (7 psi) minimum on rebuilt compressors.
A plugged pipe opening is provided in the oil relief
The plunger- or piston-type oil pump is actuated by valve for application of a pressure gauge to check
a strap riding on an eccentric on the crankshaft. Oil compressor oil pressure.
from the pump flows through the.drilled pump
plunger and eccentric and into the drilled passages An improved relief valve with a built-in accumulator
of the crankshaft. has been applied to all compressors since early 1974.

-3-
M.I. 1144

22319

PLUNGER-TYPE OIL PUMP

Crankpin Oil Passages

27827 21217

GEAR-TYPE OIL PUMP AND FILTER

Fig.4 - Lubricating System

-4-
 M.I. 1144
Pressure
Pressure Adjusting
Adjusting
Screw .
Screw

Shims

0 ydng.j
Pressure Pressure
Relief Relief
Drain Drain

0 RelJ Valv

Plugged Pipe
Opening
Relief
Valve
Oil Passage
To Crankshaft
to
Oil Filter-
Gasket
ACCUMULATOR - TYPE Surface ACCUMULATOR-TYPE
(Plunger Pump Units) (Gear Pump Units}
27828 21218

Fig.5 - Oil Pressure Relief Valve

This relief valve reduces pressure pulses. It is a direct When checking oil pressure on units that are
replacement for all existing relief valve assemblies equipped with lube oil filters, use the upper plugged
used with direct feed lubrication systems. No opening on the side of the relief valve body. The oil
crankcase modifications are required. However, for pressure relief valve is located between the filter and
proper operation, the proper gasket and mounting the crankshaft oil passages. Pressure drop across the
bolts listed in the applicable Parts Catalog should be filter has no effect on the oil pressure setting.
used.
To check oil pressure drop across the filter, take
Although the valve assembly significantly reduces pressure readings at both the upper and lower
oil pressure pulses, a pressure gauge with an openings on the side of the oil pressure relief valve
externally mounted pulsation damper should be body. Subtraction of the lower reading from the
used whenever oil pressure is measured. After the upper reading gives the pressure drop across the
pressure is checked, the locomotive should be shut filter. If the drop is as much as IO psi, the filter
down, the gauge removed, and the pipe opening should be replaced even if the replacement schedule
plugged. does not yet call for it.
Pressure readings should be taken when oil temper- CAUTION
ature is 60° C (140° F). In the event that oil The old filter gasket must be removed
temperature is lower, the oil pressure versus temper- completely in order to obtain a proper seal
ature graph shown in Fig. 6can be used to determine with the new gasket.
the corresponding pressure at 60° C (140° F). The
graph is applicable to all relief valve assemblies LUBRICATING OIL QUALIFICATION
applied to new or rebuilt compressors or supplied as
service parts after October, 1973. The graph should Since variations in operating conditions such as
not be used on earlier relief valve assemblies. ambient temperature and length of time a compressor
is loaded can influence the performance of individual
Oil pressure is varied by adding or removing shims compressor oils, a final selection of a particular
under the pressure adjusting screw on the relief brand to be used is best made by testing under actual
valve, Fig. 5. The recommended clearance between operating conditions. The oil should be tested for at
the valve body and the piston is shown in the Service least three months, and preferably six months, to be
Data. If the clearance is exceeded, and a new piston sure the variables of operation are encountered. A
will not correct the clearance discrepancy, a new compressor in new condition in respect to cylinders,
valve must be applied. On accumulator-type valves, rings, heads, and bearings should be selected for
alteration of shims is not normally required. the test.

-5-
M.I. 1144

38° C (100° F)
(I)
.....

-:::)

ro
.....
(I)
C.
43° C ( 11 0° F)
DEEP SUMP OIL PAN

E
...
Cll
49° C (120c F)
0
alca
()
..><: 54° C (130" F)
C:
(tJ
.....
u
60° C (140° F)
~5 -4 -3 -2 -1 0
Oil Pressure (PSIG) Correction Factor
Instructions: When crankcase oil temperature is below 60° C (140° F), subtract
graph readings from pressure gauge readings obtained at lower
temperatures to determine gauge pressure at 60° C (140" F).

Conditions: 1. 200 to 950 RPM

2. SAE. No. 10 weight lubricating oil.
3. Compressor loaded or unloaded.
4. Relief valve 8493807 or later.

38° C (100° F)
...
(I)
SHALLOW SUMP OIL PAN
....m
:::)

...
Q)
43° C (110' F)
C.
E
(I)
I-
49° C (120° Fl
0
(I)
1/1
!'O
()
,;,t. 54° C (130 F)
C

u
...ro
60° C (140 F)
-10 -9 -8 -7 -6 -5
Oil Pressure (PSIG) Correction Factor
Instructions: When crankcase oil temperature is below soc C (140° F), subtract
graph readings from pressure gauge readings obtained at lower
temperatures to determine gauge pressure at 60° C (140" F).

Conditions 1. 200 to 900 RPM.

2. S.A.E. No. 30 weight lubricating oil.
3. Compressor loaded or unloaded.
4. Relief valve 8493807 or lflter.
27829

Fig.6 - Correction Factor Graphs - Oil Pressure Versus Oil Temperature

6-
 M.I. 1144

At the end of the test period, the compressor and the ORIFICE TESTING
air system of the locomotive should be inspected. In
the compressor, the piston pin bushings, piston ·rhe compressor should be given an orifice test, as a
rings, cylinder walls and pistons should be inspected measure of its condition, at intervals as outlined in
for lacquer deposits. Discharge valves should also the Department of Transportation rulings.
be inspected for lacquer and hard or soft carbon
deposits. The locomotive air system can be qualified The graphs shown in Fig. 7 indicate the recommended
for lacquer accumulation by examination of the limits for the compressors covered by this instruction.
magnet valves, brake valves, and feed valves. The For part numbers of various size orifices and
presence of any lacquer, hard carbon, or excessive adapters for these tests, refer to the Service Tools
deposits of soft carbon indicates an unsuitable Catalog.
Ju bricant.
The presence of an oily substance in a feed valve
AIR FILTERS
does not necessarily mean an oil pumping air The air inlet filter or filters should be changed at
compressor, but may mean an unsuitable oil is being intervals given in the applicable Scheduled Main-
used. There are unstable ends in some oils which will tenance Program, or more frequently if operating
distill off and deposit as an oil formation at conditions require.
expansion areas such as feed valves. Generally
speaking, this substance will lacquer a shiny surface For a detailed explanation of the filters and the
rapidly. correct replacement elements required, see the
Heavy detergent oils will form hard lacquer deposits applicable Locomotive Service Manual.
in the cylinder heads and on the cylinder walls which
will result in oil carryover in the system. Heavy COMPRESSOR DISASSEMBLY
weight oils will cause excessive wear in the piston
pin bearings. Detergent or high film strength oils Before the compressor is disassembled, the exterior
would probably improve piston pin bearing life, but of the unit should be thoroughly cleaned and the
cannot be used because ring seating is affected and parts marked to ensure that each will be reapplied to
carryover into the air system has a detrimental cffcct its original location. Care should be taken when
on air brake equipment. handling parts so as not to damage otherwise
undamaged parts. When cleaning the parts, do not
Extensive experience has demostrated that heavy put main bearings, crankshaft. connecting rods,
detergent oils or mineral oils with unstable ends will valves. pistons or piston pins in same basket with
not satisfactorily lubricate compressors. In several other compressor parts.
instances of compressor failure, examination of
failed parts has shown that failure resulted from the Cylinder heads, cylinders, crankcases, end plates,
use of unsuitable oils. This has been confirmed by handhole covers, suction and discharge elbows,
the fact that upon changing to an oil suited to the manifolds, and cast iron intercoolcrs should be
application, compressor failure has not recurred. placed m a cleaning solution and left there a
WBG MODEL COMPRESSORS
w w 140
(.,'.) I I I I I I I
:) Use orifice 0.28125
(.,'.)
:::::> ~ Use orifice O 359 (23/64") .,,/ .I
~
(.,'.)
(9 32") in 1 /16" plate ~ in 1 · 16" plate
./
.r /
/
12.0 l9 120 I

(/)
CD
ff)
CD / /"
....I ....I

w w 100
~c.:,y . /
a::
:J
a::
:::::>
~0
\.,~ .,,,..~
~
(/)
(/)
(I)
(I) e:,c.:,Y 1/v~
~ ~~~(;
w 80 IJJ 80
a:: a::
a.. a.
a: a::
/ ~~~
0~
0 0 60 I'" c;
ii: > V
w w
C: / I
tfJ
w 40'---'-......L.--J'---'--'---1~..L---<-.----'-------'-__._--'
(I)
w 40
V
a:: cc
400 500 600 700 800 900 1000 400 500 600 700 800 900 1000
COMPRESSOR SPEED RPM COMPRESSOR SPEED · RPM
15698
Fig.7 - Compressor Orifice Test Limits

-7-
M.l. 1144

sufficient length of time to ensure proper cleaning. SAFETY VALVE TEST

After removal from the cleaning solution, these AND ADJUSTMENT
parts should be wire brushed and magnetic-particle
inspected for defects. A safety valve, Fig. 8, is provided to relieve excessive
pressure buildup in the intercooler. This valve must
The pistons, crankshaft, and connecting rods be tested and properly adjusted.
should be thoroughly cleaned (DO NOT WIRE
BRUSH) and magnetic-particle inspected for
defects. Exha7 Op:;ng
After magnetic-particle inspection all parts should
be rewashed and demagnetized before reassembly.
Lift
Pin
I. Remove pipe plug at bottom of crankcase to
drain lube oil. Drain compressor cooling water
by draining locomotive system. Regulator
Ring
Setscrew
2. Remove all piping assemblies and both handhole
covers. Regulator
Ring
3. Remove air filter, air intake manifold, crankcase
breather, oil pressure relief valve, safety valve,
and suction and discharge elbows.

4. Remove intercooler assembly.

5. Remove cylinder heads and cylinder assemblies.

21222

6. Remove connecting rod cap bolts, and pull

Fig.8 lntercooler Safety Valve
piston and connecting rod assemblies off of
crankshaft.
Test Procedure
7. Remove the oil pump and oil pump eccentric (if
applicable) from crankcase. In testing safety valves, it is essential that the air
supply be adequate (at least 330 liter [20,000 cu in.]
8. Remove end plate bolts and pull end plates off reservoir) with piping to the valve not less than the
the crankshaft. size of the pipe thread fitting on the end of the valve.
If restricted feed is used, the restrictions must not be
9. Remove crankshaft from crankcase. less than l I mm (7 / 16'') in diameter. If air supply is
not adequate, the valve cannot be set properly.
10. Individual assemblies can now be disassembled
by following instructions covering the particular
assembly. The valves must not lift before the specified lift
pressure, and the blowdown of the valve must not
INTERCOOLER exceed 69 kPa (10 psi). The valve must be fully
assembled when the test is made.
CLEANING
It is recommended that the intercoolers be removed
The valves should lift at a static air pressure between
at overhaul time, and cleaned inside and out. Oil 441 and 455 kPa (64 and 66 psi).
film inside the intercooler, or an accumulation of
dirt, will materially reduce its efficiency, with the
possibility of excess moisture being carried into the Adjustment
locomotive air system.
A valve which does not lift or reseat within the
The intercoolers should be cleaned using an specified pressure ranges should be disassembled
inhibited alkaline or solvent cleaner and water. and thoroughly cleaned with a solvent or caustic
After cleaning, flush thoroughly with hot water, and cleaner. (DO NOT USE A WIRE BRUSH.)
blow dry. Replace any damaged parts.

-8-
 M.L 1144

Reassemble the valve with a small amount of light 3. Clean the plunger and ring. Check that the ring
oil between the valve disc and the valve body. Apply operates freely in its groove.
a mixture of light oil and graphite on the lever pivot
and lift pin. 4. Clean and inspect the interior of the upper
plunger cover.
Adjust the lift and reseating pressures of the valve to 5. Apply a small amount of fine lapping compound
those given under Test Procedure. Adjust the lift to the angle seat on the plunger. Insert the
pressure by adjusting the pressure screw to change plunger in the cover and lap the angle scats of
spring tension on the disc. Adjust the reseating the plunger and cover.
pressure by loosening the regulator ring setscrew
and adjusting the regulator ring. After the adjustments 6. After lapping the seats, remove the plunger and
have been made, the setscrew and the hood should clean both the plunger and cover. Remove all
be lockwired and sealed. compound.

UNLOADER VALVES 7. Apply light grease comparable to petroleum

jelly to the cover, plunger, and ring. Reassemble
The piston-type unloader valves, similar to Fig. 9, the parts, using new gaskets under the cover cap
are used on the compressor to hold the intake or and the upper plunger cover.
suction valves off their seats to stop compressor
pumping when the main reservoir air is at the proper DISCHARGE AND SUCTION VALVES
pressure. Each cylinder has one discharge valve, Fig. 10, and
one suction valve, Fig. 11. Each valve is a cage-like
assembly consisting of a bumper, a seat, springs,
Cap and two concentric discs. The dies are installed
Gasket
between the bumper and seat and are held against
Hinq
the scat by springs that fit into recesses in the
bumper. The assembly is held together by a single
centrally located bolt.
Cover In a discharge valve assembly the springs are above
Plate the discs and hold them down against the seat. In a
Bolts suction valve assembly the springs arc below the
discs and hold them up against the seat. Discharge
valves on compressors made prior to May I, 1975,
and all suction valves, contain six springs, three for
each disc. Discharge valves on compressors shipped
Lower since May I, 1975 have nine-spring valves, three on
Lower __ Unloader the inner disc, and six on the outer disc. The springs
Unloader~k~.2!'·"":.==:::::;;~=.'!""==.=a~ ------ Plunger for the nine-spring valves are a helical design with
Plunger buttons on the ends that ride against the discs.
Spring

278]1
Bolt
t
I
@ Valve Discs

•
Fig.9 - Piston-Type Compressor Unloader Valve I Springs
8
Disassemble and service the valves as follows:

1. Remove the unloader valve assembly and cap

from the suction valve cover plate. Then
remove the cap and gasket from the upper
•• Bumper
Seat
plunger cover. I
21224
2. Remove the plunger assembly from the upper
plunger cover. Fig.10 - Discharge Valve Assembly

-9-
M.I. I 144

REMOVING SUCTION VALVES

Bolt'
LOW PRESSURE

Valve Discs 1. Remove the cover plate bolts, Fig. 9.

2. Remove the unloader and cover plate as an

assembly.

3. Remove the suction valve assembly, then cover

Seat the valve opening.
21225

Fig.11 - Suction Valve Assembly

HIGH PRESSURE

Special valve holders that facilitate air compressor 1. Loosen the crown nuts, Fig. 13, approximately
valve maintenance are available. These valve two turns.
holders ensure proper rigidity and minimize the
posibility of damage while work is being done on the
valves. For holder part numbers see Service Data at 2. Remove the cover plate bolts, and remove the
the back of this instruction. cover plate and unloader as an assembly.

3. Make certain that the clamp setscrews have

REMOVING DISCHARGE VALVES been loosened sufficiently to provide clearance
between the screws and the valve clamp upon
I. Back off the crown and setscrew, Fig. l 2, at the
reassembly.
center of the cover plate.

2. Remove the cover plate bolts and remove the 4. Remove the clamp.
cover plate.
5. Remove the suction valve assembly, then cover
3. Remove the valve clamp. the valve opening.
4. Remove the discharge valve assembly. Unloading
Valve Cap
5. To prevent entry of foreign material, cover the
valve openings.

Cover
Setscrew Plate
Lower
Gasket Unloader
Plunger - - Gasket
Clamp
Cylinder Lower
...-Head Lower -~unloader
U nloader _ _NhRr- Plunger
Pl unger
Discharge Spring
Valve Suction
Assembly G asket-~ttc.i Valve
~i.tiifi Assembly
21226
Bumper -=!LU~~~~~~
Assembly 21227
Fig.12 - Discharge Valve Removal Fig.13 Suction Valve Removal

- 10 -
 M.I. 1144

SUCTION AND DISCHARGE While inspecting valve seats refer to dimensions in

VALVE DISASSEMBLY the Service Data.

Valves can be taken apart to remove the springs and Valve Bumper
valve discs by removing the nut and lockwasher or
the cap bolt. The valve parts should then be cleaned Inspect valve bumper for cracks or excessively worn
thoroughly. areas. See the Service Data for dimensions.

VALVE RECONDITIONING Valve Springs

Valve Discs New valve springs should be used when reconditioning

valves. The springs should have a slip fit in the
The valve discs should be replaced if a wear step has bumper holes. A spring that fits loosely in the
formed. The following information is provided to bumper hole will wear rapidly on the bottom coil,
qualify a disc for reuse. promoting spring and disc breakage. If the spring is
not set squarely in the bottom of the hole, it will bind
A valve disc that shows no defects requires only and cause wear on the O.D. of the upper coils. This
cleaning and should not be lapped or ground. can be avoided by using a rod that is slightly smaller
than the 11 mm (7 / 16") diameter of the spring hole,
If a disc must be lapped to remove some minor and square on the end for compressing the spring
defects, even pressure should be placed on the disc. solid on the bottom. Springs that are too tight will
The valve disc should not be pressed with the also bind in the holes and cause wear on the upper
fingers, as the pressure will be applied only on small coils. Springs should be compressed after installation
areas. A disc can be sprung enough with finger to check for freedom of movement.
pressure to cause a wavy finish that will allow the
valve to leak. Cleaning

The disc should be placed in a holder that will After reconditioning and inspection, all valve parts
distribute the pressure evenly while lapping. A should be thoroughly cleaned for reassembly.
simple holder can be made from a flat steel plate cut
out to a depth of about 2/ 3 the thickness of a disc. VALVE REASSEMBLY

The disc should not be lapped to its seat. If the disc is Discharge Valve
not perfectly flat, the seat will be given a wavy
surface. The disc should be lapped on a perfectly flat Any discharge valves held in place with stud and nut
lapping plate. The lapping compound should be should have the stud replaced with a cap bolt. This
very fine so as to put an almost mirror finish on the will eliminate removing the stud each time a valve is
disc. lapped.

Occasionally, a valve disc which has had a long I. Hold bumper assembly in one hand with spring
period of service will stop rotating. If the disc pockets facing up.
remains in one position long enough, the valve
springs will wear rings in the disc. Discs in this 2. Place springs in place, with large diameter
condition should be discarded. The wear rings, if inserted into spring pocket, and place inner and
deep enough, are weak spots that can develop into outer valve discs on their respective springs.
cracks. Also, a valve disc which has had considerable
service may have a wear step in it. A disc in this 3. Invert the seat assembly and position it on the
condition should be discarded. Minimum valve disc discs.
thickness should not be less than th!lt stated in the
Service Data. 4. Hold this assembly together, apply the cap bolt,
and tighten to 115 - 129 N· m (85-95 ft-lbs)
Valve Seats torque.

r Valve seats must be completely free of any nicks,

and the edges should be square and sharp. If a valve
seat requires lapping. It should be lapped to a
Suction Valve

l. Hold the bumper assembly, spring pockets up,

master plate using a fine compound that will give a and place the inner and outer valve disc springs
shiny, scratch free surface. in their pockets.

- 11 -
 M.I. 1144

2. Place the respective discs on their springs. In compressors with single ended crankshafts the
plug in the oil passage at the stub of the crankshaft is
3. Carefully place the seat assembly over the discs. orificed for feeding oil to the main bearing. In units
with double ended crankshafts oil is fed to the main
4. Apply the cap bolt and tighten to 115 - 129 N'm
bearing by an orifice plug in the nearby end of the
(85-95 ft-lbs) torque.
crankpin oil passage. Units equipped with gear-type
Using a blunt-nosed piece of wood inserted through pumps may have, in addition, an orifice plug in the
crankpin oil passage end near the pump drive and
the valve opening, check that the valved ics are free
driven gears. Make sure that the orifices in the plugs
to move. Check for leaks by filling valve pockets
are absolutely clean. When installing, check the
with fuel oil.
orifices for proper position, Fig. 14. Take care when
If valve assemblies are not to be used immediately, tightening that the wrench does not pinch the orifice
they should be oiled and wrapped to keep them shut. Check after tightening by running a wire
clean. If the valves are to be stored, they should be throught the orifice or feeding a solvent under
pressure into the crankshaft lube oil inlet opening.
protected against rust.

CRANKSHAFT INSPEC1"ION

CLEANING The main bearing surfaces of the crankshaft should

not receive any wear and should not be less than
If the crankshaft is removed for any reason, it 85.75 mm (3.376") diameter.
should be given a thorough cleaning with solvent,
particularly during any overhaul work, since On units equipped with a plunger-type oil pump, the
metallic particles may lodge in the oil passages. All oil pump eccentric surface should not be scored,
rifle drillings must be cleaned thoroughly. tapered, or out-of-round in excess of 0.013 mm
(.0005''). The runout of the crankshaft should not
The main drilling of the crankshaft consists of two exceed 0.25 mm (.010") at the main bearingjournal,
intersecting passages. One of these passages is with the crankshaft located in centers.
parallel to the crank pin and is plugged at both ends.
These plugs are provided to aid in cleaning and must The crankpin on the crankshaft should not be more
be removed. A long-handled bristle brush having than 0.038 mm (.0015'') out•of-round, or worn to
slightly over a 8 mm (5/ 16") diameter is recommended less than 88.80 mm (3.496") diameter. If it is
for cleaning passages. During scrubbing, solvent damaged, or worn beyond above limits, it can be
should be directed into the passages under approxi- reconditioned by grinding, provided the surface will
mately 170 kPa (25 psi) pressure. Washing and clean up to 0.76 mm (.030'') undersize.
brushing must be repeated until the oil passages and
crankshaft are absolutely clean. After cleaning, be If the crankshaft has grooved seal surfaces, use
sure to replace the passage plugs which were synthetic oil seal kit 8367712 at the oil pump end and
removed. kit 8367711 at the opposite end. These kits include a
Orifice {Point Toward Orifice (Point Away Orifice {Point Toward Orifice (Point Away
Crankshaft ft) From Crnnkshaft <f.) Crankshaft Cf.) From Crankshaft ff.}
Crankpin Crankpin

-,,----
' '
' '' '
' '
' ''' , 1----.1
' '
/
/

,,
/
',
'',,,,. ,,~ ' ' ..
' /

Oil Pump Counter- Oil Pump Counter-

End weight End weight

SINGLE ENDED CRANKSHAFT DOUBLE ENDED CRANKSHAFT

Fig.14 Orifice Plug Applications 2783 2

- 12 -
 M.l. 1144

renewable wear sleeve which is to be pressed over Rifle drilled connecting rods must be used on units
the crankshaft to provide an optimum seal riding which idle at 200 RPM or lower. All rifle drillings
surface on the crankshaft. Also included is a must be cleaned thoroughly. A long-handled bristle
synthetic oil seal to operate with the 3 mm (1 /8"} brush having slightly over an 8 mm (5 / 16"} diameter
oversize shaft, provided by the wear sleeve. is recommended for cleaning passages. During
scrubbing, solvent should be directed into the
1. To apply wear sleeve, the shaft must be passages under approximately 170 kPa (25 psi)
clean and seating surface must measure 82.55 ± pressure.
0.038 mm (3.250" ± .0015').

2. Shaft surface must be coated with a liquid CYLINDERS

sealant or gasket cement.
CLEANING AND INSPECTION
3. Wear sleeve must be pressed into correct
position with arbor or flat plate against sleeve The cylinder should be thoroughly cleaned after
end. Do not hammer on thin edge of sleeve or removal, prior to any inspection or reconditioning.
wear sleeve may become warped or out-of- Examine the cylinder for score marks or ridges at
round. the end of the ring travel surface. Inspect cylinders
for a maximum out-of-round condition of 0.03 mm
4. Remove excess sealant. None should be left on (.00 l "). Also check cylinder diameter to ensure
finished working surface. correct clearances with the correct size piston.

5. Fill the cavity between the two seal lips with a Accumulated cylinder and piston wear will increase
good quality grease. piston to cylinder clearance, a limiting factor at the
time of reapplication. No cylinder should be
6. Install the seal with the name and number side matched with a new or used piston with a piston-to-
or the lip side facing the outside of the cylinder clearance exceeding the limit given in the
compressor. Service Data at the rear of this publication.
All used crankshafts will have some damage in the For example, with a WBO low pressure cylinder
seal area and it will be advantageous to use the kit, worn to a maximum diameter of 200.139 mm
as no crankshaft rework will be necessary in the seal (7.8795"), a piston not less than 199.923 mm
area. (7.8710") diameter must be used. Obviously, with a
cylinder worn to this diameter the minimum
CONNECTING RODS diameter shown in the specifications for a rebuild
piston cannot be used since the maximum clearance
Connecting rods used in the compressors are
of 0.216 mm (.0085") would be exceeded. If
equipped with precision bearing inserts. The
cylinders are worn excessively, they should be
bearing inserts should be replaced at the time of
re bored to oversize increments of 0. 25 mm ( .0 I 0"}. It
overhaul or any time their condition warrants
has been found to be more economical to rebore
replacement.
them to 0.25 mm (.010''), 0.51 mm (.020"), or 0.76 mm
The connecting rods and bearing shells should be (.030'') oversize.
fitted to the crankshaft before the crankshaft is
installed in the crankcase. Clearance limits are given If cylinders are worn to the extent that they would
in the Maintenance Data at the end of this require more than 0.76 mm (.030'') reboring, it is far
publication. The connecting rod bearing-to- more satisfactory and economical to replace them
crankshaft journal clearance can be checked by the with new cylinders or those rebored to the regular
use of Plastigage strips. oversizes.

CAUTION REBORING
Connecting rod insert bearing 8083586 must
not be used in compressors that have gear-type When reboring is necessary the cylinders should not
lube oil pumps; that is, units that have be rebored to their final size. They should be
crankshaft with a radius between the crank pin rebored to 0.05 to 0.08 mm (.002" to .003'') under
and web. Narrower bearing 8496981 must be their final size to allow enough stock for proper
used in gear pump equipped compressors in honing. If less stock is left, the boring marks will not
order to clear the radii that are at the crank pin be completely removed when the cylinder is honed
shoulders. to size.

- 13 -
M.I. 1144

HONING I. Wash cylinder with soap and hot water using

stiff fiber brush to clean cylinder bore and
After reboring, the cylinders should be honed for flanges.
the final finish. A honed finish of 0.64 to 1.01 microns
(25-40 microinchcs) is desired, with a crosshatch of 2. Swab each cylinder thoroughly with a clean rag
25° to 35°. The proper microinch finish can be dipped in IOW engine oil.
obtained from stones ranging from 180 to 280 grit.
Sec the equipment list at the rear of this publication 3. Wipe out cylinder with dry clean cloth.
for the proper cylinder bore honing set.
4. Repeat Steps 2 and 3 until clean white cloth can
Fig. 15 shows a cylinder wall at various stages of the be rubbed on cylinder wall with no stain
cylinder reconditioning operation. Figs. 15a and appearing on the cloth. It is important to use oil
l 5b are views of a cylinder after boring and before for this cleaning procedure because the oil pulls
honing. Notice the rough finish left by the boring the abrasive particles out of the tiny pores and
tool. New piston rings installed in a cylinder with crevices in the cylinder wall. Solvents will not
this finish would be ineffective. Oil consumption remove all abrasive particles.
and blow-by would remain high because the rings
could not form a good seal. Fig. 15c is the same
cylinder after 25 strokes with a spring loaded hone. PISTONS
Although honing marks are visible, the boring
marks can also be seen. This finish is still too rough At the time of the compressor overhaul, the pistons
for piston ring seating. Fig. 15d is the cylinder wall should be removed, cleaned and inspected for excess
after the cylinder was honed to size with a rigid wear, Match the pistons with a new or used cylinder
hone. The boring marks have been cleaned up and so the diameters result in a piston to cylinder
the cross hatch pattern left by the hone is all that is clearance which does not exceed the limit given in
visible. This surface is ideal for early piston ring the Service Data at the rear of this publication.
seating.
Piston ring grooves must be square and free from
The tolerance allowed on finishing oversize re bored wear ridges. Clearance between the ring side and
cylinders is +0.03-0.00 mm (+.001"-.000"). This groove should not exceed 0.0 I mm (.004'), where
tolerance is added to the amount that the cylinder is applicable. Minor scuff marks or scratches can be
rebored. For example, if a standard 177.80 mm smoothed or rounded with a file. (Do not use a stone
(7.000") cylinder is rebored 0.25 mm (.010") or emery cloth.) All pistons that are to be used again
oversize, the finished diameter after honing should should be given a phosphate treatment as outlined
be 178.05 -178.08 mm (7 .0 I0"-7 .0 l l "). in Maintenance Instruction 1758.

Honing of cylinders at regular maintenance periods

should be avoided, except when used to remove PISTON PIN BEARING REPLACEMENT
scoring. A better practice is to remove any ridge at
the top of the ring travel by scraping, and then rough Current model compressors are equipped with a
the cylinder by hand using a No. 180 emergy cloth to prefinished bushing in the low pressure piston
produce a crosshatch pattern at an angle of 25°-35° assembly and roller bearings, ?ig. 16, in the high
to the bore. pressure piston assembly. The roller bearing-type
piston assembly requires a different piston pin and
CLEANING AFTER HONING connecting rod than piston assemblies using other
types of bushings or bearings.
Of all the operations in repairing an air compressor,
cleaning the cylinders may be the most costly one to
forget. If the cylinders are not properly cleaned after Low Pressure Piston
they are honed, the compressor will wear out in an
alarmingly short time. The tiny particles left by the When reconditioning machines, replace the low
hone Will attack the rings, cylinders and any other pressure piston pin bushings with the type removed.
moving parts in the compressor. Thus, the omission
of one procedure can eliminate all the good done by The old bushings or bearings should be pressed out
hours of labor and valuable replacement parts. To using driving tool 8231757, Fig. 17. Alternate
make certain that the overhaul will last, the methods tend to gouge the inside of piston bosses
following cleaning procedure must be used: and destroy the piston for further use.

- 14 -
 M.I. 1144

(a) Highly magnified view of bored cylinder (b) Close-up view of cylinder surface after
reveals rough finish boring.

(c) Cylinder wall after 25 strokes with flexible

(d) Proper honing leaves crosshatch pattern.
hone. Note boring marks.

12520

Fig.15 - Cylinder Wall Honing

- l5 -
M.l. 1144

Retaining
Rings
1
I t/.
Roller Bearing
15701

Fig.16 - Piston Pin Roller Bearing Application

Pulling Sleeve
\
12698

Fig.18 - Piston Pin Bushing Installation

I
Bushing
8295
High Pressure Piston

Fig.17 - Piston Bushing Removal Tool When replacing high pressure piston pin bearings,
use roller bearing assemblies, Fig. 16. Those
machines which did not previously have roller
Before attempting to replace the piston bushings, bearing assemblies will require a different piston,
check the piston to see that it is sound and free from piston pin, and connecting rod.
excessive scuff marks or wear at the following
points: The old bearings should be removed by pressing to
the center of the piston with a 51 mm (2-1 / 32'')
diameter driving tool. Use care not to gouge the
I. Piston ring grooves must be square and free inside of the piston bosses with the driving tool.
from wear ridges. Clearances between ring side
and groove should not exceed maximum A piston boss support anvil and plug for pressing in
indicated in Service Data. the roller bearings can be made as shown in Fig. 19.

Before attempting to replace the piston bearings,

2. Piston to cylinder clearance must be within check the piston to see that it is sound and free from
limits indicated in Service Data. excessive scuff marks or wear at the following
points:

3. Minor scuff marks or scratches can be smoothed I. Piston ring grooves must be square and free
or rounded with a file. (Do not use stone or from wear ridges. Clearance between ring side
emery cloth.) and groove should not exceed the maximum
indicated in Service Data.

New bushings should be applied by shrinking the 2. Piston to cylinder clearance must be within
bushing with dry ice or liquid nitrogen and heating limits indicated in Service Data.
the piston. The use of liquid nitrogen will permit
dropping bushing into piston at room temperature. 3. Minor scuff marks or scratches can be smoothed
The use of dry ice will require heating piston to 90° or rounded with a file. (Do not use stone or
to 150° C (200° to 300° F). Bushing should be emery cloth.)
dropped into outside opening of piston boss with
inner end of boss squarely seated on piston bushing 4. Wash piston thoroughly to remove any foreign
anvil 8231756, Fig. 18. material, then blow it dry with clean, dry air.

- 16 -
 M.I. 1144
57 mm ..J Tap 114" - 20
(2-1/4"): UNC Thru Drill And C'sink For
~ 3 Holes 1 /4" Flat Hd. Screw 81 mm
5mm j
3/8" , 6 mm 3 Holes f--(3·3/ 16")
(1/4") Jt I 51 mm
-....-----"r---1----..-.\(2")
<t
Ehi ::--

~i ;~
I"') E;:::_ E;..
£2_
E E
E E
L!)
E L......!_,....
(1) E-
L!).
N
0
! N=:- 25mm t==--~----1-.=-.-----I-..J.--1---------e::'.'.:--i--\--1_ ?9~r61;,1) ~ -
(1 ") Drill Hole Or Holes
Necessary To Mount 24mm
l 51 mm
(2")
On Arbor Press (15/16") 56 mm
(7-3/16")
Carburize Harden And Grind
3mm
Weld As Shown (l/8")~- 83m_m --,.J
25 mm (1")
LessFin
THRUST PLATE
-.--
j _ (3-L 4") , I
':
!
--y-4'.f~---..L-
I :',: '
:: :1·i
1 1 - - - - ' " - - - ~ ' - t ' - - - ~ - l,,_ ------.-

ANVIL

--j 11 mm
(.4o0") '-a03 mm (001 ")

102 mmR
PLUG
(4") T_ 21229
25 mm {1")
Less Fin.

Fig.19 - Piston Boss Support Anvil

5. Install inner retainer rings in piston pin boss

using internal pliers.

6. Place piston over anvil, Fig. 20, locating

piston pin boss approximately in the center of
the three countersunk '>crev.s in the top of
the anvil.

7. Place roller bearing on plug and start bearing

into piston pin bore, being sure bearing is
l parallel with pin bore.

J 8. Press bearing into piston until plug bottoms on

the 0.0. of the piston. Do not overpress plug.

Anvil/
9. Remove plug, rotate piston 180° and relocate 16703
the other piston pin boss on the anvil. Repeat
Steps 7 and 8. Fig.20 - Roller Bearing Installation

- 17 -
M.L 1144

10. After both bearings have been installed, remove cylinder. This spring and ring combination is
the piston from anvil and install the two outer applied to the top and No. 2 ring grooves of the
retainer rings. piston, with the spring above the ring.

11. Cover both ends of the piston pin bore to keep NOTE
foreign material out of the bearings until the Ring side clearance limits given in the specifi-
piston pin is installed. cations do not apply to the spring and ring
combination. Oil control rings are used in the
PISTON PIN REPLACEMENT bottom piston ring groove of all compressor
pistons.
The piston pin must be replaced if it is scored,
damaged, or exceeds clearance limits given in the High Pressure Low Pressure
Service Data. A special tool is available for piston Compression Rings
pin and connecting rod assembly, Fig. 21. This
assembly fixture 8213878 ensures proper alignment
of the piston pin and connecting rod and prevents
twisting the connecting rod when torquing the
retaining bolt to the recommended 108-136 N'm
(80-100 ft-lbs). It also positions the rod eye with the
slot machined in the wrist pin for application of the Used In 3 Used In 2
retaining bolt. Grooves Upper Grooves
(3rd Empty)
Connecting rod spreader 8214312, also shown in
Fig. 21, is used to expand the wrist pin bore of the
connecting rod so it may be aligned in the piston Oil Control Rings
assembly fixture without the use of force, which
might damage the assembly.

Connecting Rod Spreader

(8214312) Used In Bottom
Groove Both Cylinders 15704

Fig.22 - Piston Ring Assembly

To properly apply the piston rings, use the correct

ring expanding installing tool according to the
Piston Assembly Fixture piston diameter. See the Service Data for the correct
(8213878) ring expanders.

Standard size rings should be used on all standard

pistons for all bore sizes up to where a 0.25 mm
8498 (.010") oversize piston can be used. Piston rings
Fig.21 - Piston Assembly Fixture should be fitted through the bottom of the cylinders
And Rod Spreader rather than through the top, because the bottom of
the cylinder is chamfered to prevent damage to the
PISTON RINGS ring on entry, and this end wears less than the top.
Therefore, rings must have at least minimum
To aid in piston ring identification and location, the clearance at the lower end of the cylinders. Piston
various ring combinations for the compressor are rings should never be filed to obtain end clearance.
shown in Fig. 22. Compression rings are marked on
top with a pip or dimple to ensure proper application. OIL PUMP
Oil control rings are not marked as they may be
applied with either side up. PLUNGER-TYPE PUMP

Particular notice should be made of the ring and The oil pump should fit the crankshaft to the limits
spring combination used in the low pressure listed in the Service Data. If the clearance limit is

- 18 -
 M.I. 1144

exceeded, a new oil pump eccentric will be required. The area of the crankshaft that the lip of the
The oil pump plunger should be inspected for synthetic rubber seal touches should be well oiled or
scoring and excessive wear. It the clea ranee limit is greased.
exceeded as given in the Service Data, a new pump
assembly should be installed. I. On compressors equipped with plunger-type oil
pump, install the oil seals in the end plates as
explained in the "Crankshaft" section of this
GEAR-TYPE PUMP publication. On models equipped with gear-
type oil pump, Fig. 2J, first install the oil
The backlash in the oil pump drive is fixed by dowel introducing ring, piston rings, and retainer rig
pins in the oil pump mounting flange. The end play in the end plate, making sure that the retainer
in the oil pump drive shaft should be not less than ring snaps firmly in place. Then install the oil
0.03 mm (.00 I") or more than 0.10 mm (.004'l It is seals.
obtained by pulling up on the adjusting nut until this
endplay is 0.05 mm (.002") to 0.13 mm (.005"). then
advancing the nut to the nearest locking position.
If the clearance limits arc exceeded as given
in the Service Data. a new pump should be
Oil
installed. Introducing
Ring

When converting a unit from plunger-type pump to

Retainer
gear-type pump. the oil pump mounting flange will Ring
have no dowel pins to fix the oil pump backlash. lhe Bearing
backlash bet\, een the oil pump gears shou Id be
bct\\ecn .002" to .004". Complete retrofit details arc ''
given in M. l. 9621. '' '
' Crankshaft
'
'
'

OIL PRESSURE RELIEF VALVE

I he oil pressure relief valve should be completely
disassembled and thoroughly cleaned. All passages
should be blown out, using compressed air. The /

valve should then be reassembled and rc..,et as

described in the Lubricating System section.

PRESSURE GAUGES
The orifice screw should be removed and the air and
oil pressure gauges tested on a dead weight tester.
After testing, an orifice screw having an orifice
diameter not greater than O.JX mm (.015") must be Bearing
Cover Plate
installed in the gauge and staked securely in 27699
place.

Fig.23 - Gear-Pump Compressor

COMPRESSOR REASSEMBLY Oil lntroducting Assembly
The air compressors should be assembled with new
gaskets and oil seals. The bearing surfaces of the 2. Mount the main bearing inner races on the
crankshaft, main bearings, connecting rod bearings, crankshaft and the outer races in the crankcase
wrist pins, and cylinders should be adequately (oil pump end) or the end plate (opposite oil
lubricated with approved air compressor oil, as pump end). The races must be flat against the
recommended in Maintenance Instruction 1756. locating shoulder within 0.05 mm (.002").

- 19 -
M.I. 1144

3. Install the crankshaft in the crankcase with a 7. Using a piston ring compressor, mount the
gasket behind the end plate opposite the cylinders on the crankcase.
intercooler and shims at the intercooler so the
oil pocket and passage is up, providing gravity 8. The following steps should be taken before
feed lubrication to the main bearings. installing the cylinder heads to the cylinders to
ensure maximum operating performance of the
NOTE cylinder head gaskets.
If leather type oil seals are used, oil seal guide
821990 I should he employed when sliding the
leather type oil seals over the shaft keyway and a. Gasket surfaces on cylinder and heads must
shoulder on the shaft. Any burr will destroy the be free of deep scratches and foreign
feather edge of the oil seal. material. The faces of the water cooled
heads must be flat within 0.05 mm (.002").
4. Check the end thrust of the crankshaft by
exerting 1724 k Pa (250 psi) pressure alternately b. Gaskets should be dipped in or coated with
at each end of the shaft and checking shaft light motor oil prior to application, to
movement with a dial indicator. Thrust clearance permit flow of gasket and complete sealing.
should not exceed the limits given in the Service Use of heavy grease, gasket cements, or
Data. If necessary the end thrust may be graphite coatings should be avoided as they
adjusted by the addition or removal of shims impair gasket performance and life. Proper
between the end plate and crankcase. positioning of gasket should be attained by
using short studs inserted in head before
5. Install the plunger-type oil pump and oil pump application.
eccentric in the crankcase. Torque the eccentric
strap bolts to 47-61 N'm (35-45 ft-lbs). Install
cotter pins in the strap bolts and lockwire the oil 9. The valve covers on the discharge valves, and
pump mounting bolts. the unloader on the high pressure suction valves
should be installed with the valve clamp screws
Install the gear-type oil pump. Torque the released. After the covers are installed, the valve
mounting flange bolts to 62-74 N·m (45-55 ft-lbs). clamp screws should be tightened and locked in
place with the clamp screw crown nut. On the
NOTE low pressure suction unloader assemblies, care
The identifying or matching marks on the should be exercised to ensure that the suction
connecting rods, connecting rod caps, and valve cover gasket is compressed. If the gasket
both halves of the oil pump eccentric (plunger- does not compress, two gaskets should be
type pump only) must all be on the same side. applied. Do not remove the valve seat gasket.

6. Install the previously assembled piston and 10. Mount the cylinder head assemblies containing
connecting rod assembly on crankshaft. Torque the suction and discharge valves, onto the
connecting rod bolts to 197-210 N·m cylinders.
(145-155 ft-lbs). Install locknut hand tight
against connecting rod nut and tighten I 3 to 11. Install the intercooler, then tighten the intercooler,
I 2 turn. cylinder head, and cylinder mounting bolts as
explained in Step 6. Tighten cylinder head bolts
NOTE to 163-176 N·m (120-130 ft-lbs) following the
When installing the cylinders, cylinder heads, pattern in Fig. 24.
and intercooler to the compressor, be sure to
use the proper gaskets and initially tighten the 12. Install the safety valve, suction and discharge
bolts hand tight. To limit the cylinder distortion elbows, air filter, crankcase breather, oil
to a minimum the mounting bolts should be pressure relief valve, and oil filter, (if applicable)
tightened to the proper torque value as in their proper locations.
specified in the Service Data in the following
order: 13. If the unloader piping is in good condition, it
should be reused. If new unloader piping is
Intercooler to cylinder head. required, the latest type should be used. The
Cylinder head to cylinder. piping should be soap tested for leaks at 620 kPa
Cylinder to crankcase. {90 psi).

- 20 -
 M.I. 1144

To provide means of relieving air pressure while

testing compressor on locomotive, the compressor
discharge relief valve (if so equipped) should be
removed and a globe valve installed. Flexible tubing
or armored hose can be attached to the valve and
placed so that air and vapors will discharge outside
the engineroom.

As soon as the compressor is started, either on the

test stand or in the locomotive, the lube oil pressure
should be approximately 310 kPa (45 psi) with cold
oil. As the oil temperature increases, the pressure
WBG - Low And High will drop. The oil pressure should be adjusted to
Pressure
I 03 kPa - 137 kPa ( 15-20 psi) with oil temperature at
about 60° C (140° F) at 315 RPM.
27833

Fig.24 - Cylinder Head Tightening Sequence COMPRESSOR TEST BREAK-IN RUN

Before the final test runs, the compressor should be
14. If unit has water deflector piping, Fig. 25, install given a break-in run for 30 minutes at 425 RPM
the piping such that the deflectors at the high pumping against a maximum of 69 kPa (10 psi) air
pressure cylinders are positioned with the word pressure. On the test stand, a 50.8 mm (2") globe
"TOP" stamped on the deflector, on the top valve is used to exhaust the air being pumped and on
side. If the unit has the new reduced sludge, low the locomotive the newly installed globe valve and
pressure cylinders, Fig. 26, reapply the water other air drains can be used. If this does not exhaust
piping. These new units do not require a sufficient air to keep the pressure at 69 kPa ( 10 psi),
sediment removal system. the automatic brake valve can be moved to the full
release position.
15. Wipe the crankcase clean with lint-free, bound-
edge towels and install the handhole covers. If
the oil gauge and oil filter were removed from After the half hour break-in, close drain valve(s) and
the handhole cover, replace them in their let main reservoir air pressure build up to normal
proper positions. cutout setting of the unloader governor or compressor
control switch. Repeat several times to make sure
suction unloading valve parts and unloader governor
COMPRESSOR BREAK-IN AND or compressor control switch are operating correctly.
TESTING AFTER OVERHAUL If any valve fails to unload properly, shut down the
Where a customer has many air compressors to compressor and repair the defect.
break-in and test, it is recommended that a test
stand be set up. Drawings covering such an
installation will be furnished on request. File FINAL TEST RUNS
Drawing No. 343 covers a schematic piping diagram
for an air compressor test stand, and File Drawing Set unloader governor or compressor control switch
No. 603, an air compressor test stand arrangement. to cut out at 689 kPa ( 100 psi) and cut in at approxi-
If access to a compressor test stand is not possible, mately 620 kPa (90 psi). Open drain sufficently so
the compressor may be tested on the locomotive. that compressor operates at 50% load factor (i.e.,
unloaded for the same amount of time that it is
PRELIMINARY TEST PROCEDURES loaded), and run for 2 hours at 425 RPM.

Whether the compressor is to be mounted on a test

stand, Fig. 27, or tested in the locomotive, the Following the first 2 hour final run, reset unloader
following steps should be taken before starting test: governor to cut out at normal operating pressure.
Insert a temperature gauge in the pipe plug hole in Operate at 50% load factor under these normal
the crankcase to check temperature rise of lube oil. pressures for an additional 2 hours at a compressor
A 10°-150° C (50°-300°F) gauge can be used. speed of 425 RPM.

- 21 -
M.I. 1144

21231

Deflector

11£3 Deflector At High

Pressure Cylinder
At High
Pressure
Cylinder

WBO
20261 WBG 20362

Fig.25 Water Deflector System Applied To Earlier Units

- 22 -
 M.J. 1144

Fig.26 Typical Water Piping Application

(Basic Low Sludge Cylinders)

5720

Fig.27 - Typical Test Stand Installation

- 23 -
M.I. 1144

OPERATING TESTS
Audio inspections of moving parts should be made
at regular intervals during the break-in period. If
any noise (other than the normal valve click) is
The valves may then be replaced, and with the
compressor running under load, all gasket joints
should be tested for air leaks. This testing may be
done with water applied to all gasket joints with an
oil can.
,
apparent, or a regularly occurring thump can be felt
by placing hand on compressor, the cause of the After making sure that all valves are again working
noise or vibration should be corrected before properly and that all joints are tight and free from
attempting any further testing. leaking, the machine should be given an orifice test.
See Fig. 6 for orifice test limits.
The intercooler pressure, observed during a test run
while under load, should be near 380 kPa (55 psi). COMPRESSOR STORAGE
This pressure is an indicator of valve efficiency. The
pressure may vary slightly due to change in air If the place of storage is near a sea coast or in a damp
temperature or barometric pressure, but any vari- climate, it is recommended that the compressor be
ation of more than 20 kPa (3 psi) above or below given a l hour 50% load factor test run every 20-90
normal intercooler pressure is an indication of a days during the high humidity season to prevent
defective valve(s), the location of which can be minute rust areas forming on cylinders and valves.
found as follows: The experience obtained from other similar
machinery in the same climate area will assist
1. If intercooler pressure is abnormally high only materially in establishing the optimum interval
when pumping, the high pressure suction valve between storage period retest.
should be inspected.
If the tested compressor is to be kept in storage for
2. If the intercooler pressure climbs slowly when an indefinite length of time, it should be protected
the compressor is unloaded, the high pressure against rust. After slushing with anti-rust oil, wrap
discharge valve should be inspected. the breather cap and all safety valves with MIL-B-131
barrier material and seal with pressure sensitive tape.
3. If the intercooler pressure is abnormally low
when pumping and drops to zero pressure in If the compressor is to be immediately installed in a
Jess than 3 minutes when unloaded, the low locomotive, the slushing with anti-rust oil will not
pressure discharge valves should be inspected. be required.

4. If the intercooler pressure is abnormally low After the compressor has completed the recommended
when pumping, but drops only a few pounds running time and appears to be working satisfactorily,
after being unloaded 3 minutes, the low all valves should be removed and the cylinders
pressure suction valves should be inspected. inspected for scoring or scratches that might have
occurred during assembly or break-in. Brown
The low pressure discharge valves or low pressure streaks in the cylinder should not be confused with
suction valvei at fault will usually be indicated by a scratches or scoring, as this is not an abnormal
weak or erratic suction sound, abnormal blowback ·condition and these streaks disappear after the rings
from air filter, or an excessively hot low pressure and the cylinders have had sufficient running to
discharge valve cover plate. properly polish themselves together.

- 24
 M.l. 1144

SERVICE DATA
SPECIFICATIONS

Lube Oil Capacity

Shallow Sump Deep Sump
WBO 11.63 Liter (3 Gal.) 39. 75 Liters ( 10-1 / 2 Gal.)
WBG 17.03 Liter (4-1 /2 Gal.) 68.14 Liters (18 Gal.)

Valve Rework Limits

Millimeters Inches
Valve Seats Min. Max. Min. Max.
Difference between center boss
and valve disc seat 0.25 0.010
Gasket surface flat within 0.13 0.005
Gasket seat width 3.18 0.125
Valve Bumper
Distance disc seat surface below
center boss surface 3.56 3.96 0.140 0.156
Guide finger height must not be greater than center boss height.
Valve Disc
Thickness 1.32 0.052
Lift 1.98 2.59 0.078 0.102

• Dimensions For Rebuild - Low Pressure Cylinder

Millimeters
Min.
Model WBO

Max.
Inches
Min. Max.

Cylinder Height . . . . . . . . . . . . . 288.544 288.925 l l .3600 11.3750

Cylinder Inside Diameter

New 200.025 200.063 7.8750 7.8765
*Maximum 200.139 7.8795

•
Piston Diameter
New 199.898 199.923 7.8700 7.8710
**Minimum 199.809 7.8665
Clearances
Piston To Cylinder
New ...... 0.102 0.165 0.0040 0.0065
Rebuild 0.102 0.216 0.0040 0.0085
Piston Pin 0.033 0.10 0.0013 0.004
Side of oil ring to groove 0.05 0.10 0.002 0.004
***Ring Gap ........ 0.20 1.01 0.008 .040

Model WBG

~.
I
Cylinder Inside Diameter
New
*Maximum
Piston Diameter
New
177.800

177.686
177.838
177.914

177.711
7.0000

6.9955
7.0015
7.0045

6.9965
**Minimum 177.597 6.9920

- 25 -
M.I. 1144

ModelWBG
Millimeters
M in. .M.fils.:.
Clearances -
Piston To Cylinder
New 0.089 0.152 0.0035 0.0060
Rebuild 0.089 0.203 0.0035 0.0080
Piston Pin 0.033 O.lO 0.0013 0.004
Side of oil ring to groove 0.05 0.10 0.002 0.004
***Ring Gap . . . . . . . 0.18 0.007

*Using new piston at maximum diameter.

**Using new cylinder at minimum diameter.
***Install new rings whenever it is necessary to remove rings from piston or cylinder.

Dimensions For Rebuild - High Pressure Cylinder

Model WBO

Millimeters
Min. MM:
Cylinder Height 272.669 273.050 10.7350 10.7500

Cylinder Inside Diameter

New 146.050 146.088 5.7500 5.7515
*Maximum 146.164 5.7545
Piston Diameter
New 145.948 145.974 5.7460 5.7470
**Minimum 145.859 5.7425
Clearances -
Piston To Cylinder
New 0.076 0.140 0.0030 0.0055
Rebuild . . . . . 0.076 0.191 0.0030 0.0075
Piston Pin 0.03 0.064 0.001 0.0025
Side of ring to groove 0.05 0.01 0.002 0.004
***Ring Gap . . . .. 0.15 0.81 0.006 0.032

Model WBG
Cylinder Inside Diameter
New 146.050 146.088 5.7500 5.7515
*Maximum 146.164 5.7545
Piston Diameter
New 145.948 145.974 5.7460 5.7470
**Minimum 145.859 5.7425
Clearances -
Piston To Cylinder
New 0.076 0.140 0.0030 0.0055
Rebuild 0.076 0.191 0.0030 0.0075
Piston Pin 0.03 0.064 0.001 0.0025
Side of ring to groove 0.05 0.10 0.002 0.004
***Ring Gap ..... 0.15 0.006

*Using new piston at maximum diameter.

**Using new cylinder at minimum diameter.
***Install new rings whenever it is necessary to remove rings from piston or cylinder.

- 26 -
 M.l. 1144

General Clearance Data

Millimeters Inches
Min. Max. Min. Max.
Main bearing outer race to
crankcase bore or end plate -0.03 +CUB -OJ)OI +0.001

tMain bearing end (cold)

Model WHO 0.20 0.33 Cl.008 O.OIJ
Model WBG 0.26 0.38 0.010 0.015

Unloader assembl; unloader

plunger to upper plunger 0.10 0.004

(tConnecting rod bearing O.OJO CL08 0.0012 0.003

tttConnecting rod side 0.33 0.76 0.013 0.030

Plunger-type oil pump

Oil pump eccentric 0.03 0.08 0.001 0.003
Oil pump plunger to body 0.03 0.064 0.001 0.0025

Gear-type oil pump

Rotor to housing 0.05 0.002
Idler pm to idler bushing 0.05 0.002
Idler to crescent 0.10 0.004

Oil pressure relief valve - clearance

between valve body and piston 0.013 0.08 0.0005 0.003

ttf end clearance is more than maximum limit, remove one 0.13 mm (.005'1 shim and recheck.
ttDo not file cap or rod or use shim stock to tighten. When maximum clearance is reached. install new inserts.
ttn otal clearance for all rods on one crankpin.
Connecting Rod Parallelism And Twist
Connecting rod bores must he parallel \\ithin 0.041 mm (0.0016'1 in l."i2 mm (6'').
Connecting rod twist must not exceed 0.041 mm (0.0016") in 152 mm (6'').

. ,.
- 27 -
M.l. 1144

EQUIPMENT LIST
Part No.

Hone Set ........................ . 8039177

Holder - Stone
(Used with 8039177 hone set on high pressure cylinders) 8102249
Ring Expanders
(5-3 / 4" cylinder) 8205284
(7- 7 / 8" cylinder) 8205286
(7" cylinder) 8205285
Piston Ring Guide
( 5-3 / 4" cylinder) 8205491
(7- 7 / 8" cylinder) 8205493
(7" cylinder) 8205492
Piston Assembly Fixture 8213878
Connecting Rod Spreader 8214312
Valve Holder 8214755
Oil Seal Guide . . . . . 8219901
Piston Bushing Anvil 8231756
Piston Bushing Puller .. 8231757
Piston Bushing Groove Scraper 8231758
Lifting Eye-Bolt . . . . . . . . 8159760

TORQUE VALUES
Recommended torque values for air compressor fasteners are indicated in the charts that follow. These torque
values are based on threads that are clean and free of burrs and grit. The cleaning solvent (if used) should have
a trace of lubricant.

- 28 -
 3/8"
15 _ ,-716 Clamp Set Screw'
3/8"
15 - ,-11 6 Acom Nut
5/8" 1 1
60 · Clamp Set S c r e t :
r- \
'

t~"io11 Acorn Nut

,..._u-'-'-··'

1/2" X 1'1J/
45 55 j

,I I 1
-ir,5/8" 1/4"x1/2"
l\"~I X 1-1/r
8 - 10
§ ___. . . - )
··--t. [.:!30-150

['.
!'-' ;~ All Torque Values In Foot p ounds
- .. -_ [ Ft-lbs x 0.1383 k .
• · ~ I
·'"'-'<~,,}:'( ,· Ft-Lbs ·, 1 ·3558 g ,m)
N·m.
27835

Torque Chart - WBO

Gear Type Lub CO~mlplete With
e I Pump
 318" · 16 Clamp Set Screw
15 · 17
3/8" · 16 Acorn Nut
15 - 17

-.__________ 11 /2" X 1"

"145 - 55

·[3/8" X 7 /8"
w 20 - 30
0

3/4" X 2"1-
130 · 150j
Not Shown
5/8" X 6-3/4"}-
100 120 Eye Bolt All Torque Values In Foot Pounds
3/8" X
20 _ 30
2''1Jlnspect1on Plate ( Ft-Lbs x 0.1383 kg·m ')
\ Ft-Lbs x 1.3558 = N·m 1
1/4" X 1/2"! . .
8 _ 10 -,-D1pst1ck

3/4". - 16 x 5-3/8'}-Counterweight
.
300 330

5/8" ,c 1-1/4';-i
'~
130 150
112" x 1-3/4"
f ~<2?-~~~~~s::s:ss:~
. ss "<;:;\ssi '"\.I
Tighten Finger Tight ····
70 . 75 ···Brg. Cover Plate Cap Screws
3/4" X 1-3/4", Against Regular Nut
130x150 J Then Tighten 1 /3 To 1 /2
Turns More 27836

Torque Chart - WBG Complete With

Gear Type Lube Oil Pump

) )
 l ,.i
3/8" - 16 Clamp Set Screw]
15 · 17 '''
3/8" · 16 Acorn Nut 3/8" X 7/8"
15 - 17 20 30
5/8" - 11 Clamp Set Screw r5/8" X 1-3/4"
60
3/8" 7/8"
X 5/8" - 11 Acom Nut ~0-70
20 - 30 60 - 70
-{112" x 1-1 /8"
45 - 55

5/8" X 1-3/4"
50- 70

3/8" X 7/8"
20 - 30

Not Shown
5/8" X 1-1/4" 1/4"x7/~8'
130-150 5 -7
~1130
r5/8" X i-1/2"
1 50
--
t---'---r--~·::.,,
3/8" x 2'}-inspection Plate
1/2" X 1-1/4'} .1_• 20- 30
45 55 Tighten Finger Tight
Against Regular Nut
~--->-.--<1/2"-20 Then Tighten 112 To 0
_x1~ 314 '}H.P. Head Bolt
35 Min. IThen Tighten Nut Unti, Slots lJ /3 Turns More
Line Up With Hole In

All Torque Values In Foot Pounds

/ Ft-Lbs x 0.1383 = kg·m)
\ Ft-Lbs x 1.3558 = N·m 27837

Torque Chart - WBO Complete With

Plunger Type Lube Oil Pump
M.1. l 144

1 i:)" .x 1-1 8"

I { 45. 55

Not Shown:
Top And Bottom Tank To Core Screw
5;16" X 1-1;4" 8 18 :L/838

lntercooler Torque Chart

• • • • A Service Department Publication • • • •

E lactro-Motive Division Of General Motors La Grange, Illinois 60525

- 32 - Litho In U.SA