Troubleshooting - Hitachi ZX27U-2 Operator's Manual

3. Hydraulic System
Trouble
Insufficient power: all actuators
Insufficient power: front attachment
Machine does not travel smoothly.
Machine mistracks
Insufficient swing power or jerky
upperstructure swing
NOTE: Contact your authorized dealer for any inspection, adjustment, repair, and/or replacement as required.

TROUBLESHOOTING

Cause
• Insufficient engine power
• Excessively worn hydraulic
pump
• Main relief valve failure
• Hydraulic oil is low
• Suction filter restriction
• Failure or incorrect pressure set-
ting of main or pilot relief valve
• Damaged hydraulic cylinder
packing
• Damaged cylinder piston or cyl-
inder tube
• Too tight track (sag)
• Foreign matter, such as rocks,
stuck in the tracks
• Counterbalance valve failure
• Travel motor performance drop
• Track sag is not equal on both
sides
• Hydraulic pump performance
drop
• Oil leak inside control valve
• Hydraulic pump performance
drop
• Low pressure valve setting
• Swing motor performance drop
• Swing bearing seizure
• Foreign matter sticking in brake
valve
• Oil leak inside control valve
11-2
Solution
• Inspect and repair
• Replace
• Re-adjust pressure setting, or re-
place
• Add hydraulic oil
• Clean or replace
• Re-adjust pressure setting, or re-
place
• Replace cylinder packing
• Replace cylinder piston, cylinder
tube, or the cylinder
• Adjust track sag
• Remove foreign matter
• Replace
• Replace
• Adjust track sag properly (and
equally on both sides)
• Replace
• Replace the control valve
• Replace
• Adjust pressure setting, or replace
• Replace
• Lubricate or replace swing bear-
ing
• Clean the brake valve
• Replace the control valve