VOLVO CONSTRUCTION EQUIPMENT
SERVICE MANUAL
l60F/L70f/L90F
CONTENT
5 Brakes
Descriptions
MORE CARE. BUILT IN.
Foreword
This booklet is part of a complete service manual. Read the fore‐
word in the service manual.
WARNING!
Always read the booklet Safety before proceeding.
VOE 21 A 1002940
1
Content
50 GENERAL
500 Comprehensive info about brakes
Braking system, description ........................................................................ 5
Pump 2, hydraulic (passive) brake pressure charging ............................. 7
Pump 3, electrically controlled brake pressure charging ......................... 7
Braking ..................................................................................................... 7
Brake test ................................................................................................. 8
Software ................................................................................................... 9
55 PARKING BRAKE
550 General, common info about 551 - 554
Parking brake, description ........................................................................ 11
Application of parking brake .................................................................. 13
Release of parking brake ....................................................................... 13
Software ................................................................................................. 14
3
BRAKE
50 GENERAL
500 Comprehensive info about brakes
Braking system, description
Regarding: L60F, L70F, L90F
The machine has a hydraulic brake system, divided into two cir‐
cuits, one for the front axle and one for the rear axle.
The hydraulic brake system consists of a foot brake valve and an
accumulator block with three accumulators. One accumulator is
for the front circuit, one accumulator is for the rear circuit and one
accumulator is in common.
The accumulators are precharged with nitrogen gas and their
purpose is to store pressure and to make sure that the braking
capacity is safeguarded.
The brake system is supplied via the central valve with hydraulic
oil from Pump 3 (P3) or Pump 2 (P2). P3 is located on the engine
power take-off on the left side of the machine. P2 is located on
the transmission power take-off on the right side of the machine.
P3 supplies the radiator fan and ensures that the brakes are
charged during transport operation. P2 supplies the brake system
passively when the working hydraulics is used and when P2 is
not supplying the steering system with oil.
If the brake pressure becomes too low, information about this is
shown on the operator display unit.
The front and rear axles are equipped with wet disc brakes.
Brake cooling is achieved in that each brake disc is equipped with
pump impeller, which works as a circulation pump for the axle oil.
The axles have built-in brake disc wear indicators.
See also 263, Cooling fan, description, 370, Wiring diagram
501and 990, Hydraulic diagram, complete.
5
Fig.1
1 Central valve
2 Cooling fan motor
3 Accumulator block, brakes
4 Parking brake
6
Pump 2, hydraulic (passive) brake pressure charging
Pump 2 (P2) feeds the central block and from there primarily sup‐
plies the steering with oil. The pressure-limiting valve for max.
steering pressure limits the maximum working pressure of the
steering. When the steering is "saturated" with oil, the priority
spool in the central valve shifts to supplying brake pressure charg‐
ing, servo system and working hydraulics. When the working
hydraulics is used and the pressure exceeds existing system
pressure in the brake circuit, the brake accumulators will be pas‐
sively charged via the pressure-reducing valve for brake pres‐
sure.
Pump 3, electrically controlled brake pressure charging
If the pressure in the working hydraulics is insufficient, the brake
system is instead charged by the fan pump (P3). Pump 3 supplies
oil to port (PF) on the central valve and from there to the cooling
fan motor via port (PFF). The hydraulic oil flow is guided via pro‐
portional valve PWM2601, which controls the pressure, to the LS-
connection on the pump via port LSF.
When V-ECU registers a pressure below 12 MPa from SE5218,
brake pressure charging is initiated. The voltage to PWM2601
increases. At the same time MA5502 closes. The hydraulic oil flow
to the fan is then limited by a restriction.
When the brake pressure has risen to approx. 15 MPa, the brake
pressure charging is interrupted. The V-ECU lowers the voltage
to proportional valve PWM260, MA5502 opens and the cooling
fan returns to the rotational speed it had before the brake pressure
charging was initiated.
If the requirement for cooling is great, the cooling fan motor
receives a large flow of oil producing a high pressure in the circuit.
If the pressure exceeds the existing system pressure in the brake
circuit, the brake accumulators will be charged passively.
If the pressure in the brake accumulators is too low, sensor
SE5218 warns of this, via the instruments.
Braking
When the brake pedal is pressed down, the connection to the
axles is opened. The hydraulic oil can then flow from the pumps
via the central valve and the accumulator block for the brakes to
the axles where the brakes are applied.
The foot brake valve is of the proportional type, which means that
the output brake pressure is proportional to the pedal angle. The
valve is divided into two circuits. One circuit acts on the front axle
brakes and the other on the rear axle brakes. The maximum brake
pressure out to the axles is reduced compared with the pressure
that is delivered to the foot brake valve. Adjustment of the reduced
brake pressure is performed on the underside of the valve by
increasing or decreasing the pedal stroke.
7
Brake test
With the aid of the operator display unit it is possible to carry out
a simple test of the brakes, see 387, Information display, ser‐
vice. Instructions for the procedure is shown on the display unit.
The bake test calculates the retarding ability of the machine to
gain information about the condition of the brakes. The measuring
result and the average value of the brake pressure is shown on
the display unit. If the measuring is not approved, no measuring
results will be shown on the display unit.
When the speed exceeds 10 km/h (6 mph) after completed test,
the measuring result disappears until a new test is carried out.
The three latest approved measurings are saved for presentation
on the display unit under the service menu.
8
Software
Brake pressure, monitoring (accumulator)
Input signals Conditions for output functions Output functions
- Brake pressure low - Brake pressure low True - Warning
True/False Engine Off Low brake pressure
- Engine On/Off Machine moving On
- Machine moving On/ - Brake pressure low True
Off Engine On
The following applies in case of incorrect input signals:
Input signal Assumed value in case of a fault
Brake pressure Low
Engine On/Off Off
Machine moving On
Brake pressure (accumulator), reference
Input signals Conditions for output functions Output functions
- VCADS Pro parame‐ General conditions for the function
ter GZG - VCADS Pro parameter CWO ≠”0”
- Brake pressure,
- Brake pressure < 90 bar - Brake pressure low True
SE5218
- Brake pressure > 90 bar - Brake pressure low False
- Brake pressure < 125 bar - Brake pressure charging
low True
- Brake pressure > 125 bar - Brake pressure charging
low False
- VCADS Pro parameter CWO ”0” - Check
Parameter error
In case of faulty input signals, the output signals are considered
to be faulty.
Brake pressure charging
Input signals Conditions for output functions Output functions
- Brake pressure low - Brake pressure charging low True for 60 seconds - Warning
True/False - Engine On Brake system failure
- Brake pressure - Brake pressure charging low False - Brake pressure charging
charging low True/ - Engine On requested
False - Brake pressure low True - Warning
- Engine On/Off Brake system failure
- Brake pressure low True for 10 seconds - Brake pressure charging
- Engine On requested
- Brake pressure charging low True
- Engine On
In case of a faulty input signal Engine On/Off, it is considered to
be On.
In case of a faulty input signal Brake pressure charging low, brake
pressure charging must be requested.
In case of a faulty input signal Brake pressure low, it will be con‐
sidered False
9
Brake pedal applied
Input signals Conditions for output functions Output functions
- Output brake pres‐ - Output brake pressure < 0.5 MPa - Brake pedal applied Off
sure, SE5205 - Output brake pressure ≥ 0.5 MPa - Brake pedal applied On
In case of a faulty input signal, the output signals are considered
to be faulty.
Stop lights
Input signals Conditions for output functions Output functions
- VCADS Pro parame‐ General conditions for the function:
ter GZR - VCADS Pro parameter GZR “1”
- Brake pedal applied
- Brake pedal applied Off - Brake pedal applied Off
On/Off
- Brake pedal applied On - Brake pedal applied On
- Stop lights, LA5201 and
LA5202 light up
Brake test
Input signals Conditions for output functions Output functions
- Speed, SE4307 - Brake test activated On (via the display unit). - Brake test started On
- Output brake pres‐ - Speed < 20 km/h (12.4 mph)
sure, SE5205 - Speed 15 km/h (9.3 mph) at the time of the decelera‐ - The time (clock) and output
- Clock tion. brake pressure is stored.
- Brake test activated
On/Off - Speed 5 km/h (3.1 mph) at the time of the decelera‐
tion.
- Completed brake test. - Brake test information is
shown on the display unit
within 0.5 seconds.
In case of faulty input signals for speed, output brake pressure or
clock (time) the output signals are considered to be faulty.
In case of faulty input signal for Brake test activated, it is consid‐
ered to be Off.
10
55 PARKING BRAKE
550 General, common info about 551 -
554
Parking brake, description
Regarding: L60F, L70F, L90F
The parking brake is a disc brake positioned externally on the
transmission front output shaft.
The parking brake is applied and released with switch SW5501.
When the lower end of SW5501 is pressed in, the parking brake
is applied. To release the parking brake, the catch on SW5501
must be released.
Regardless of the position of switch SW5501, the parking brake
is applied when the engine is turned off. When the engine is
started and the lower end of SW5501 is not pressed in, the switch
must first be pressed in and then released, if the parking brake is
to be released.
Fig.2 SW5501
NOTE! If the engine is started and the lower end of SW5501 is
not pressed in, the parking brake will be released automatically,
when either of the directional gears is selected and the engine
speed exceeds 1600 rpm.
See also 370, Wiring diagram 501 and 990, Hydraulic diagram,
complete.
11
Fig.3
1 Central valve
2 Accumulator block, service brakes
3 Parking brake
12
Application of parking brake
When the lower end of SW5501 is pressed in or if the engine is
turned off, MA5501 becomes de-energised. The oil from the
hydraulic pumps (via the central valve and brake accumulator
block) cannot pass through the parking-brake valve to the parking
brake, which means that the parking brake becomes applied
because of the spring force. SE5503 senses no pressure and
sends signal to the V-ECU about this, which will cause the control
lamp for the parking brake to light up (if the ignition is on).
Release of parking brake
When SW5501 is released, MA5501 becomes energised. The oil
from the hydraulic pumps (via the central valve and brake accu‐
mulator block) can pass through the parking-brake valve and the
parking brake is pressurised. The hydraulic oil pressure then
overcomes the spring force and the parking brake is released.
Also SE5503 registers pressure and sends signal about this to
the V-ECU whereby the control lamp for the parking brake is
extinguished.
If the operator selects directional gear forward or reverse, even
though the parking brake is applied, a warning will be shown on
the operator display unit. If the warning is ignored, the parking
brake will be released automatically, when the engine speed
exceeds 1600 rpm.
13
Software
Electric parking brake
Input signals Conditions for output functions Output functions
- Ignition switch, Machine stationary - Parking brake applied “ON”.
SW3301 - Engine Off MA5501 de-energised and
- Speed, SE4307 - Speed < 5 km/h (3 mph) SE5503 without pressure.
- Parking brake - Ignition switch in position 0
applied
- Engine speed,
Machine in starting position - Parking brake applied “ON”.
- Engine Off MA5501 de-energised and
SE2701
- Speed < 5 km/h (3 mph) SE5503 without pressure.
- Engine On/Off
- Directional gear in position Neutral - Warning lamp, parking
- Directional gear
- Ignition switch in position 1 brake
- Switch, parking
brake, SW5501 Machine in operation with directional gear in position - Parking brake applied “ON”.
Neutral MA5501 de-energised and
- Engine On SE5503 without pressure.
- Switch, parking brake in position Applied - Warning lamp, parking
- Directional gear in position Neutral brake
Machine in operation with directional gear in position - Parking brake applied “ON”.
Forward or Reverse MA5501 de-energised and
- Engine On SE5503 without pressure.
- Switch, parking brake in position Applied - Warning lamp, parking
- Directional gear in position Forward or Reverse brake
- Red central warning
- Warning
Applied parking brake
Release of parking brake, when the machine is in - Parking brake applied
operation and the parking brake is applied with the “OFF”. MA5501 energised
parking brake switch and SE5503 pressurised.
- Engine On
- Switch, parking brake in position Released
- Directional gear in position Neutral
Safety function “Release of parking brake” when the - Parking brake applied
machine is in operation and the parking brake is “OFF”. MA5501 energised
applied because the engine has been turned off. and SE5503 pressurised.
- Engine On
- Switch, parking brake in position Applied
- Directional gear in position Forward or Reverse
- Engine revolutions <1600 rpm
- Logic diagnostics Application of parking brake - Check
- When MA5501 becomes de-energised, SE5503 Parking brake failure
should be without pressure within 3 seconds Check at next stop
Release of parking brake
- When MA5501 becomes energised, SE5503 should
become pressurised within 10 seconds
The following applies in case of incorrect input signals:
Input signal Assumed value in case of a fault
Engine “On”
Ignition switch, SW3301 “ON”
Engine speed, SE2701 <1600 rpm
Directional gear "Neutral"
Speed, SE4307 0 km/h (3.7 mph)
14
Parking brake alarm
Input signals Conditions for output functions Output functions
- VCADS Pro parame‐ General conditions for the function - Red central warning
ter HWU “ - VCADS Pro parameter HWU “ON” - Warning
- Parking brake Park brake NOT applied
- Engine On
applied
- Parking brake applied “OFF”
- Engine On/Off
- Load operator seat On >3 seconds
- Load operator seat,
SE8502
The following applies in case of incorrect input signals:
Input signal Assumed value in case of a fault
Engine “On”
Parking brake applied “ON”
Load operator seat Function turned off
VCADS Pro parameter HWU “OFF”
Parking brake applied
Input signals Conditions for output functions Output functions
- Parking brake pres‐ - SE5503 without pressure - Parking brake applied “ON”
sure, SE5503 - SE5503 pressurised - Parking brake applied
“OFF”
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To From
Volvo Construction Equipment AB ....................................................................................
Customer Support Division
Dept. CEE ....................................................................................
S-631 85 Eskilstuna
Sweden ....................................................................................
e-mail: servicemanuals@volvo.com
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Ref. no. VOE 21 A 1002940 English
Printed in Sweden 2007-01 CST
Volvo, Eskilstuna
