Damcos LPU: Troubleshooting Guide LPU Service Manual
February 2017 SM 8000-100-01 Ed 04
55
Noise from pump, but only at high pressure
Reason: • Air in the pump if actuator has not been properly de-aired. Check oil level in tank.
• Too small tank volume for large actuators or long pipes in system.
• Piston in pump is sticking.
A pump piston is operating too tightly and does not follow the ball bearing curve during move-
ment. At relatively high pressure it is pressed out hydraulically. The sound can disappear at start-
ing-up. Otherwise pump is dismounted and pistons and rotor are checked for coverings or burrs.
Note! If pump rotor has to be replaced the stator version has to be checked (check placement
and number of expanding plugs). If stator versions are different both rotor and stator must
be exchanged (complete pump set, see “Replace Pump in LPU” on page 93).
Noise from pump at both high and low pressure
Reason: Motor and pump are not co-axial, pump stator is not mounted firmly in the block.
Action: • Check steering pins between blocks.
• Dismount pump and check that remounted stator is perpendicular to valve block.
See “Replace Pump in LPU” on page 93 for more information.
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