Hitachi EX1900-5 Operator's Manual page 271

Problem
Oil Foams
Low or No Oil Pressure
No Hydraulic Functions
(Noise from pumps)
Hydraulic Cylinders Operate
but Cannot Lift Load
TROUBLESHOOTING
HYDRAULIC SYSTEM
Cause
Air leak in line from reservoir to pump
Kinks or dents in oil lines
Wrong oil
Water in oil
High or low oil level
Wrong oil
Improperly adjusted hydraulic
components
No oil in system
Worn cylinder packings
Relief valve
Hydraulic pump
Lack of hydraulic oil
Damaged suction line or hose
Clogged suction filter
Hydraulic pump worn
Main relief valve pressure low
Hydraulic oil level low
Suction screen plugged
Pump suction line leaking
11-11
Solution
Repair leak or see your authorized
dealer.
Check lines.
Use correct oil.
Change oil.
Correct level.
Use correct oil.
See your authorized dealer.
Fill with correct oil.
See your authorized dealer.
See your authorized dealer.
See your authorized dealer.
Add oil.
See your authorized dealer.
Clean.
See your authorized dealer.
See your authorized dealer.
Add oil.
Clean strainer and system.
Inspect suction line.