Operation and maintenance manual

Section 250-0120
1
SM 2163 7-02
BRAKING SYSTEM - Pressure Relief Valve
DESCRIPTION
Numbers in parentheses refer to Fig. 1. The pressure
relief valve can be identified as item 4 in Section 210-
0005, COOLING SYSTEM SCHEMATIC.
Mounted on the disc brake oil cooler casing on the
right hand fender, the pressure relief valve houses a
direct acting relief valve cartridge (2).
The pressure relief valve is installed between the triple
gear pump and the two speed control valve. Pressure
relief valve limits the maximum pressure in the disc
brake cooling circuit.
OPERATION
Numbers in parentheses refer to Fig. 1.
The pressure relief valve houses a direct acting
pressure relief cartridge (2), set at 200 bar (2900 lbf/
in²). The relief cartridge (2) controls pressure supplied
to brake cooling circuit by triple gear pump, bypassing
excess pressure back to the main hydraulic tank.
REMOVAL
Numbers in parentheses refer to Fig. 1.
WARNINGS
Hydraulic fluid pressure will remain within the
system after engine shut down. Operate the
treadle valve continuously until the pressure
has dissipated before carrying out any work on
the braking system or serious injury could
result.
To prevent personal injury and property
damage, ensure wheel blocks, blocking
materials and lifting equipment are properly
secured and of adequate capacity to execute
the job safely.
1. Position the vehicle in a level work area, apply the
parking brake and switch off the engine.
2. Block all road wheels and place the battery master
switch in the 'Off' position. Place steering lock bar in
the 'Locked' position.
3. Remove guard from rear of disc brake oil cooler.
Refer to Section 210-0050, DISC BRAKE OIL
COOLER.
4. Remove blanking cap from remote drain line at the
bottom of the hydraulic tank. Install a length of hose on
remote drain fitting, open drain cock and drain
hydraulic oil into a suitable container. Close drain
cock, remove hose and reinstall blanking cap.
5. Clean pressure relief valve and surrounding area
with a suitable solvent. Identify and tag all hydraulic
lines connected to pressure relief valve, to aid in
'Installation'.
6. With suitable containers available to catch leakage,
disconnect hydraulic lines. Fit blanking caps to all
open lines.
7. Remove bolts (5) and washers (3 & 4) securing
pressure relief valve to disc brake oil cooler casing.
Remove pressure relief valve from casing.
DISASSEMBLY
Numbers in parentheses refer to Fig. 1.
1. Note location of all hydraulic connectors and
adaptors and remove from valve body (1).
2. Remove relief valve cartridge (2) from valve body
(1).
INSPECTION
Numbers in parentheses refer to Fig. 1.
1. Clean all parts with a suitable solvent and dry with
compressed air.
2. Check ports threads and make sure they are not
SM - 2759
Fig. 1 - Pressure Relief Valve
1 - Valve Body
2 - Relief Valve Cartridge
3 - Washer
4 - Lockwasher
5 - Bolt
1
5
3
4
2