120 SECTION 35 - HYDRAULIC SYSTEM
7.2 FAULT FINDING
GENERAL
LOADER
PROBLEM CAUSE CORRECTION
All systems fail to operate Pump drive inoperative
Low oil level
Restricted pump suction line
Check and repair as necessary.
Check and top up.
Inspect the suction line and the tank
and repair as necessary.
Slow operation or loss of power in
all circuits
Worn pump
Restricted pump suction line
Load sense pressure relief valve
incorrectly adjusted
Hydraulic speed solenoid valve
inoperative
Perform pump performance test and
replace/reseal as necessary.
Inspect the suction line and the tank
and repair as necessary.
Make a system pressure test.
Make a system pressure test.
PROBLEM CAUSE CORRECTION
The lifting system fails to operate,
is slow or loses power
Valve spool leakage
Piston seals leaking or cylinder
barrel damaged
Examine lift section of loader control
valve assembly for wear or scoring.
Examine/reseal piston and gland.
Bucket fails to operate, is slow or
has loss of power
The relief valves are stuck open,
set to a too low value or there is a
leak in the seat
Valve spool leakage
Piston seals leaking or cylinder
barrel damage
Check the bucket system relief
valve.
Examine bucket section of loader
control valve assembly for wear or
scoring.
Examine/reseal piston and gland.
Cylinder leak (spools in neutral) Damaged piston barrel
Internal valve leakage
Examine/reseal piston and gland.
Examine appropriate valve section
of loader control valve assembly for
wear or scoring.
Hesitation in the raising
movement of the loader
attachment or of the bucket
cylinders when the control is
initially actuated
Load check valve between
control valve sections damaged
Disassemble and inspect.
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