Operation and maintenance manual

Section 210-0045
3
SM 2152 6-02
solenoid fails to energise, hydraulic pressure will be
allowed to rise at the inlet port (P). This will default the
engine cooling fan to run constant at the higher speed
setting, thus safeguarding the engine against high
operating temperatures.
Solenoid Coil Rating: 22 Watt continuous.
2. The solenoid cartridge valve (1) to which the
solenoid is attached. Failure is only likely to occur due
to contamination in the system. The valve (1) is a low
leakage device and any contamination may cause
either damage to the components or cause
components to stick in position. Failure may be more
difficult to detect due to the different modes of failure.
Damage to the components will allow a progressively
increasing leakage, eventually resulting in some flow
not being shut off when the solenoid is selected.
Sticking components could hold the system at either a
low engine cooling fan speed or a high fan speed
depending on what position the cartridge valve (1) is
stuck.
3. The relief valve (2). Contamination is the only likely
cause of failure, causing damage to the relief valve (2)
seat. Failure will be difficult to detect as the result of
contamination damage is likely to be loss of flow
across the relief valve (2) seat at pressure. This loss
of flow is difficult to detect until it becomes very
excessive. For example when the solenoid valve (1) is
energised, the relief valve (2) may not act due to the
contamination, allowing pressure to be raised at the
inlet port (P). This would default the engine cooling fan
to the higher speed setting, even although preset
parameters have not been attained.
4. The check valve (3). Contamination is the only likely
cause of failure, causing damage to the non-return
valve seat. Failure will be difficult to detect as the
result of contamination damage is likely to be loss of
flow across the check valve (3) seat at pressure. This
loss of flow is difficult to detect until it becomes very
excessive.
REMOVAL
Numbers in parentheses refer to Fig. 1.
WARNING
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. Operate
treadle valve continuously to relieve pressure in the
braking system.
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 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.
4. Clean low temperature unloader valve and
surrounding area with a suitable solvent. Identify and
tag all hydraulic lines connected to the low
temperature unloader valve, to aid in 'Installation'.
5. With suitable containers available to catch leakage,
disconnect hydraulic lines. Fit blanking caps to all
open lines.
6. Remove electrical harness connector from solenoid
valve (1).
7. Remove bolts and lockwashers securing the low
temperature unloader valve to the hydraulic cradle.
Remove low temperature unloader valve from the
cradle.
DISASSEMBLY
Numbers in parentheses refer to Fig. 1.
1. Note location and position of all hydraulic
connectors and adaptors prior to removing them from
valve body.
2. Remove knurled nut from end of the centre shaft of
the solenoid. Slide off solenoid coil.
3. Unscrew solenoid cartridge valve (1) from valve
body. Extract cartridge valve (1).
4. Remove relief valve (2) from valve body.
5. Remove check valve (3) from valve body.
INSPECTION
Numbers in parentheses refer to Fig. 1.
1. Clean all parts with a suitable solvent and dry with
compressed air.
Cooling System - Low Temperature Unloader Valve