U20-3, U25-3 WSM Hydraulic system (Service section)
IV-S-6
c. Pump
Problem Cause Correction
1. The engine gets overloaded.
1) Engine rpm higher than specified.
2) Pressure higher than specified.
3) Pump internal parts seized or damaged.
1) Readjust as specified.
2) Readjust as specified.
3) repair or replace the pump.
2. The pump flowrate drops
extremely with too low
discharge pressure.
1) Engine rpm too low.
2) Pump coupling defective.
3) Pump internal parts seized or damaged.
1) Readjust the rpm.
2) Repair or replace the pump coupling.
3) Repair or replace the pump.
3. Unusual noise or unusual
vibrations occur (cavitation
phenomenon).
1) Air or water mixed in hydraulic oil.
2) Suction strainer clogged.
3) Suction pipe clogged or throttled.
4) Attached pump in trouble (if provided).
5) Piston shoe poorly crimped.
6) Pump loosely mounted.
7) Coupling defective.
1) Retighten the circuit connections, the
suction pipe in particular. Replace if
water is mixed in.
2) Clean or replace the suction strainer.
3) Correct the suction pipe.
4) Repair or replace the attached pump.
5) Replace the piston assembly.
6) Mount correctly.
7) Replace the coupling.
4. There is oil leak.
1) O-ring or sheet packing defective.
2) Oil leak from oil seal edge.
1) Replace the O-ring or sheet packing
(install as specified).
2) Replace or repair the oil seal or shaft.
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