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