Form No. R92.00 Rev. 10/03
Problem
Possible Cause
Look For
Noisy Pump
Misaligned shaft
Faulty installation
Distortion in mounting
Axial interference
Faulty coupling
Mechanical fault in pump
Piston and shoe loose or failed
Bearing failure
Incorrect port plate selection or index
Eroded or worn parts in
displacement control
Erosion on
Air in fluid
Refer to above
barrel
Cavitation
Refer to above
and
port plate
High wear
Excessive loads
Reduce speed or pressure setting
in pump
Contaminant particles in fluid
Improper filter maintenance
Filter too coarse
Dirty fluid introduced to the system
Reservoir or breather cap open to
atmosphere
Improper line replacement
Improper fluid
Fluid too thick or too thin for operating
temperature range
Fluid breakdown due to age, temperature
or shearing effects
Incorrect additives in new fluid
Reduced additive effectiveness due to
chemical aging
Improper repair
Incorrect parts, procedures, dimensions
or finishes
Unwanted water in fluid
Condensation
Faulty breather/strainer
Heat exchanger leaking
Faulty clean-up practice
Water in makeup fluid
Pressure
Cogging or erratic load movement
Mechanical considerations
shocks
Slow acting relief valve
Replace with fast acting relief valve
Worn relief valve
Repair or replace, as needed
Worn compensator
Repair or replace, as needed
Insufficient line capacitance (line volume,
Increase line size or length
line stretch, accumulator effects)
Fluid
Excessive pump leakage
Recheck case drain flow,
overheats
repair as needed
Fluid too thin, minimum operating viscosity
60 SUS (10Cst)
Improper assembly
Faulty relief valve
Set too low (compared to load
or compensator)
Instability caused by back pressure,
or worn parts
Faulty compensator
Set too high (compared to relief)
Worn parts
Faulty heat exchanger
Water turned off, or insufficient flow
Ambient water temperature too high
Fan clogged, restricted or inoperative
Mud or scale buildup
Intermittent hydraulic fluid flow through
exchanger
4
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TROUBLESHOOTING GUIDE
