OPERATION 3.25 TROUBLE SHOOTING
239
3.25.2 HYDRAULIC SYSTEM
Problem Probable cause
Poor hydraulic system perfor-
mance
● Hydraulic oil not at operating temperature.
● Engine speed too low.
● Reservoir low on oil
● Restrictions in lines
● Cooling circuit, pump control system and/or pilot control circuit
defective.
● Internal leakage (control blocks, valves or power units.)
● Pressure lines twisted or kinked
● Spool not in full stroke.
● Relief valve defective, or out of adjustment.
● Worn cylinders.
● Defective hydraulic pump.
Excessive oil temperature
● Low oil level
● Incorrect viscosity or type of oil
● Hydraulic oil cooler clogged with dirt.
● Oil cooler fan defective or wrong speed.
● Cooling circuit defective
● Pump control system defective
● Spool not in full stroke.
● Internal leakage (control blocks, valves or power units)
● Worn pump components
● Job conditions (high temperature of materials being handled)
Jerky motion of power cylinders
● Piston rod bent
● Piston sticking
● Inside diameter of cylinder tube partially increased or scored
● Air in control circuit
● Oil too cold
● Valve spool sticking, centering springs defective
● Pump and/or engine control system defective
● Valve of power circuit defective
Noise when slewing
● Insufficient lubrication of swing ring gear and/or slewing connection.
● Slewing connection mounting bolts loose
● Drive pinion worn
● Swing gear bearings worn
● Sun gear or planetary pinions worn
● High pressure circuit valves defective
● Anti-cavitation valves sticking
Excessive oil foaming
● Air in hydraulic system
● Poor quality oil
● Excessive by-passing of oil over relief valves
● Pressure hoses badly twisted or kinked
● Restricted oil flow due to foreign matter
● Breather on the reservoir clogged.
● Relief valve improperly adjusted
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