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Section E
15 - 10
Hydraulic System
- Variable Flow
Fault Finding Contents
Introduction
High or low system pressure
Pump stays at high pressure
Pressure or flow obtained at one port only
No pressure or flow at either port
High work port leakage
Leaks between sections
Sticking spool
Detent will not hold
Electrical detent will not hold
Poor performance, slow operating speed and/or
low maximum stall speed
PROBLEM:
POSSIBLE CAUSE:
CORRECTIVE ACTION:
PROBLEM:
POSSIBLE CAUSE:
CORRECTIVE ACTION:
PROBLEM:
POSSIBLE CAUSE:
CORRECTIVE ACTION:
PROBLEM:
POSSIBLE CAUSE:
CORRECTIVE ACTION:
PROBLEM:
POSSIBLE CAUSE:
CORRECTIVE ACTION:
9803/3280
Hydraulics
Fault Finding
Page No.
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High or Low system pressure.
1) Wrong pressure and/or flow regulator valve settings. 2) Loss of pilot signal due to shuttle
failure.
1) Readjust regulator valves. 2) Operate individual services to determine which shuttle is at fault,
refer to Service Procedures, Variable Flow Pumps, Shuttle Valve Signal Network -
Testing.
Pump stays at high pressure.
1) Sticking main spool. 2) Sticking compensator spool.
1) See 'Sticking Spool' guide. 2) Remove & clean compensator spool.
Can only obtain pressure or flow at one port.
1) Dirt in primary shuttle or damaged o-ring.
1) Remove & clean shuttle, inspect o-ring and replace if required.
No pressure or flow at either port.
1) Dirt in secondary shuttle.
1) Shift one spool at a time with blocked ports until faulty section found, remove shuttle and
clean, inspect o-ring and replace if required.
High work port leakage.
1) Spool not centred. 2) Dirt in port relief valve.
1) Check centring springs. 2) Remove & clean relief valve.
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Introduction
This section details the possible faults that may be found
with the loader and backhoe valve blocks. The faults listed
only appertain to valve blocks fitted on variable flow
hydraulic machine systems (Rexroth valves).
1
B ef o re yo u b eg in f ault f ind ing , read t he Saf et y
information at the beginning of this manual.
2
Make simple checks before say, stripping a major
component.
3
Make sure that the hydraulic fluid is at correct working
temperature (50 ° C, 122 ° F).
4
What ever t he fault , c hec k t he c ond it ion of t he
hydraulic fluid. Drain and replace if necessary.
5
Make any relevant electrical checks before moving on
to the hydraulics.
6
Be sure to remove ALL contamination and if possible
identify its origin. It may be part of a component from
elsewhere in the circuit.
7
Rep lac e any seals suc h as ' O' ring s b ef o re re-
assembling hydraulic components.
Section E
15 - 10
Issue 1
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