25 - 1
Fault finding
As a first step towards locating a fault, carry out the
following checks.
1 Check the hydraulic filter for the presence of excessive
foreign materials. The nature of the foreign materials
could yield a clue as to the source of damage or wear.
2 Check the flow rate and condition of the oil drained
from the pump.
3 Check for abnormal sounds and vibration.
4 Check the pressure at each of the pump pressure test
points.
Section E Hydraulics
9803/6020
Section E
25 - 1
Issue 1
Hydraulic Pump
Symptom
1 Pump is producing abnormal noise.
2 Insufficient flow.
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 oil
viscosity.
d Input shaft rotation speed abnormally
high.
e Component mechanically damaged,
Bearing etc.
a Input shaft rotation speed decrease.
b Oil temperature abnormally high.
c Oil viscosity abnormally high.
d Switching valve or actuator leakage.
e Inadequate pump displacement.
f Power adjustment screw is loose.
g Air is being drawn in due to low oil
level in the hydraulic oil tank.
h Pump cavitation due to a clogged
suction strainer.
j Excessively low oil temperature, or
pump cavitation due to high
viscosity.
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.
Adjust the rotation speed.
Replace the damaged parts
Reset the pressure.
Flush the circuit.
Change the hydraulic oil.
Adjust the rotation speed.
Stop the operation and re-check after the
oil temperature has dropped.
Check that the correct hydraulic oil for the
ambient conditions is being used. If not,
renew the oil.
Replace the switching valve and actuator.
Replace the pump.
Reset and lock.
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.
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