Hitachi Zaxis 17U-5A Operator's Manual page 237

Problem
Only one actuator is inoperable.
Only one cylinder is inoperable or has
no power.
Hydraulic oil temperature increases.
Oil leak from low pressure hose
TROUBLESHOOTING
Cause
Broken control valve spool
Embedded foreign matter in valve spool
Broken pipe and/or hose
Loose pipe line joint
Broken O-ring at pipe line joint
Broken actuator
Faulty pilot valve
Faulty pilot circuit line
Broken oil seal in cylinder
Oil leak due to damage to cylinder rod
Faulty pilot valve
Faulty pilot circuit line
Low set pressure of main or port relief valve
(boom, arm and bucket)
Stained oil cooler
Insufficient engine fan belt tension
Loose clamps
11-5
* Replace
* Repair or replace
* Repair or replace
Retighten
* Replace
* Repair or replace
* Replace
* Repair or replace
* Repair or replace
* Repair or replace
* Replace
* Repair or replace
* Adjust and replace
Clean
Adjust
Retighten
* Mark: Consult your authorized Hitachi dealer.
Solution