HYDRAULIC SYSTEM 5540F/YB5515 SERVICE MANUAL
4-4 Published 10-21-2010, Control# 198-04
Table 4-2
Lift Circuit Troubleshooting
Overheating of hydraulic oil. Wrong operation (running over the
load sense relief pressure setting for
long periods).
Change procedure of operation.
Dirty filters. Change filter. See Preventative
Maintenance, Chapter 5.
Oil too light. Use correct oil.
Low oil level. Check and add oil.
Dirty oil. Change oil and filters. See
Preventative Maintenance, Chapter 5.
Foam in hydraulic oil tank. Leak in system. Check O-ring on pump inlet. Check for
leak in system and correct.
Wrong type of oil. Use correct oil.
Low oil level. Check and add oil.
Bad seal in pump, motor or cylinder. Overhaul or replace.
Short life of pump bearings, shafts, etc. Dirt in oil. Change oil and filter more frequently.
Wrong type of oil. Use correct oil.
Pump leakage (external). Bad seal on pump shaft. Replace shaft seal.
Bad seals between pump sections
(Swing & Steering).
Replace seals.
Difficult to engage valve spools. Dirt or foreign material between spool
and valve bore.
Remove and clean valve spool valve
and bore.
Broken spring (spool return). Replace spring.
Distortion or damage to valve spool. Replace valve section.
Problem Possible Cause Remedy
Problem Possible Cause Remedy
Lift cylinder does not extend or retract. Control valve not actuated. See Difficult to Engage Valve Spools.
Not enough oil from pump to operate
the cylinder.
See Loss of Movement During
Operation.
Bad leak in hydraulic swivel. Replace seals.
Load sense relief valve held open by
dirt on valve seat.
Disassemble and clean or replace the
load sense relief valve.
Cylinder extends, but does not retract. Malfunction in holding valve. Replace the holding valve. DO NOT
ADJUST.
Restriction in hose to control valve. Check and correct.
Cylinder retracts but does not extend. Malfunction in anti-double blocking
electrical system.
See Electric System.
Bad cartridge in anti-double blocking
solenoid valve.
Replace cartridge.
Restriction in pilot control line to control
valve.
Locate and repair.
Faulty controller. Repair or replace.
Reference Only
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