Operation and maintenance manual

Section 210-0005
SM 2154 Rev 1 10-03
1
COOLING SYSTEM - Brake Cooling System Schematic
DESCRIPTION
Numbers in parentheses refer to Figs. 2 through 5.
The braking system on the machine uses brake cooling
oil to cool the brake packs. This cooling oil is separate
from the hydraulic oil used in the main hydraulic
systems.
A brief description of the individual components used in
the brake cooling system are listed below. Detailed
service and operating instructions can be found in the
relevant component sections of this manual.
Service Brakes
Refer to Section 165-0015, BRAKE ASSY - OCDB.
The service brakes are of the enclosed, forced oil-
cooled multiple disc type. The service brakes are
actuated by hydraulic oil as specified in Section 300-
0020, LUBRICATION SYSTEM. DO NOT use BRAKE
FLUID (J 1703). Multiple discs within the brake packs
are cooled by brake cooling oil as specified in Section
300-0020, LUBRICATION SYSTEM.
The brake pack is bolted to the stub axle and houses a
sandwich of friction discs splined to a hub rotor. There
are six friction discs in each of the front axle brake
packs, four in the centre and rear axle brake packs.
When the treadle valve is actuated, hydraulic oil enters
the brake pack and forces the piston against the
rotating friction discs which react with stationary stator
plates. The stator plates are retained by scalloped
tangs at the outside diameter, which in turn transfers
the reaction torque to the rigid outside housing, slowing
or stopping wheel rotation.
In an emergency situation, application of the park/
emergency valve will actuate the service brakes and
the parking brake to bring the machine to a halt. In this
condition, a restriction in the 'Px' line from the brake
manifold valve will slow oil flow from the parking brake
allowing the service brakes to actuate momentarily
ahead of the parking brake.
Triple Pump (1)
Refer to Section 250-0040, TRIPLE PUMP.
The triple pump is mounted off the transmission power
takeoff. It is a triple gear type pump, which supplies
various circuits:
a) front section (closest to driveshaft) supplies brake
actuation circuit and engine cooling circuit.
b) middle section combines with front section to
supply engine cooling circuit.
c) rear section supplies the brake cooling circuit.
The triple pump is assembled for left hand (anticlockwise)
rotation, as viewed from the driveshaft end.
Note: Never drive a pump in the wrong direction of
rotation, as pump seizure may result.
Brake Coolant Tank (2)
Refer to Section 250-0025, BRAKE COOLANT TANK.
The brake coolant tank is the reservoir for the brake
cooling oil. It is mounted off the left hand frame rail in
front of the fender and is secured in three places.
Integral with brake coolant tank assembly are filter
assembly, oil level sight gauge, strainer, manifold
block, low pressure relief valve (8) and access covers.
Located on top of the tank is filler cap, breather and
walkway plate. Heatshields are fitted to front and side
of tank.
Low Temperature Unloader Valve (3)
Refer to Section 210-0045, LOW TEMPERATURE
UNLOADER VALVE.
The low temperature unloader valve is located on the
hydraulic cradle, below the hydraulic diverter tube.
The low temperature unloader valve receives hydraulic
supply from the engine cooling section (mid section) of
the triple gear pump (1). An integral two way solenoid
cartridge controls flow to the hydraulically driven engine
cooling fan. The pressure relief valve controls circuit
pressure to a preset 205 bar (2970 lbf/in²).
Pressure Relief Valve (4)
Refer to Section 250-0120, PRESSURE RELIEF
VALVE.
Mounted on the disc brake oil cooler casing on the right
hand fender, the pressure relief valve limits the
maximum pressure in the brake cooling circuit. The
pressure relief valve is installed between the triple gear
pump (1) and the two speed control valve (5).
Two Speed Control Valve (5)
Refer to Section 250-0065, TWO SPEED CONTROL
VALVE.