12 - 2
Fault finding (cont’d)
Section E Hydraulics
9803/6410
Section E
12 - 2
Issue 1
Hydraulic Pump/Regulator
Symptom
3 Pump is producing abnormal
noise.
4 Engine overload - engine
operates at extremely low
speeds or stops.
5 Oil leakage.
Possible cause
a Air is being drawn in due to low
oil level in the hydraulic oil tank.
b Pump cavitation due to a
clogged suction strainer.
c Excessively low oil temperature,
or pump cavitation due to high
viscosity.
d Resonance with external parts.
a The torque regulator is set too
high.
b The filter incorporated in the
pump is clogged.
c The pilot oil passage and orifice
inside the regulator are clogged,
or some parts are thermally
seized or damaged.
d Seizure or wear of pump internal
parts.
a Oil seal failure originating from
an increased drain flow and
raised pump internal pressure.
b Oil seal failure originating from
restricted drain line and raised
pump internal pressure.
Remedy
Top up the hydraulic oil and bleed air
from the system.
Clean the strainer. If excessively
clogged, flush the hydraulic system
and/or renew the hydraulic oil
Check that the correct hydraulic oil for
the ambient conditions is being used.
If not, renew the oil.
Check mounting bolts and tighten if
necessary.
Readjust the regulator.
Clean the filter. If excessively clogged,
flush the hydraulic system and/or
replace the hydraulic oil.
Readjust the regulator. If no changes
are observed, dismantle the regulator
for inspection and repair.
Dismantle and renew worn or
damaged parts.
Dismantle and renew the oil seal,
taking particular care not to damage
the lip when fitting the new oil seal.
Change the drain lines so that
pressure no higher than 3 bar (43
lb/in
2
) is exerted on the oil seal.
Renew the oil seal. (Take particular
care not to damage the lip when
fitting the new oil seal.)
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