System noise or vibration
Item
Description
Action
Oil in reservoir
Insufficient hydraulic fluid will lead to cavitation.
Fill reservoir to proper level.
Air in system
Air bubbles will lead to cavitation.
Look for foam in reservoir. Check for leaks on inlet side
system loop and repair. Afterwards, let reservoir settle until
foam dissipates. Run system at low speed to move system
fluid to reservoir. Repeat.
Pump inlet vacuum
High inlet vacuum causes noise. A dirty filter will
increase the inlet vacuum.
Inspect and replace filter as necessary. Check for proper
suction line size.
Shaft couplings
A loose shaft coupling will cause excessive noise.
Replace loose shaft coupling or replace pump or motor.
Shaft alignment
Misaligned shafts cause noise.
Align shafts.
System response is sluggish
Item
Description
Action
Oil level in reservoir
Insufficient hydraulic fluid causes sluggish response.
Fill reservoir to proper level.
Multi-function valves pressure
settings
Incorrect pressure settings affects system reaction
time.
Adjust or replace multi-function valves.
Pump inlet vacuum
High pump inlet vacuum reduces system pressure.
Measure charge inlet vacuum. If high, replace inlet filter.
Prime mover speed
Low engine speed reduces system performance.
Adjust engine speed.
Charge and control pressures
Incorrect charge or control pressures affects system
performance.
Measure charge and control pressures and correct if
necessary.
System internal leakage
Internal leakage reduces system pressure.
Check for leakage in O-rings, gaskets, and other fittings.
Service Manual
Series 90 Pumps
Troubleshooting
520L0818 • Rev 0101 • August 2015
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