7. HYDRAULIC SYSTEM
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(2) Main pump
Defective pump oil seal or plate seal
Defective pump
Change to oil of proper viscosity
Operate pump at proper
temperature.
Find the cause of air bubbles and
take necessary measures.
Replace with new ones.
Replace pump with a new one.
Problem
No oil discharged from gear
pump
Cause
Low oil level in oil tank
Clogged suction tube or strainer
•
Worn pressure plate
•
Worn bearing
•
Defective plate seal, bushing seal
or back-up
Gear pump pressure won’t
rise
Noisy gear pump
Oil leaks from pump
Maladjusted relief valve
Air being sucked
Collapsed suction hose or clogged
strainer causes cavitation
Air being sucked due to a loose suc-
tion side joint
Too viscous oil causes cavitation
Air bubbles in oil
Remedy
Add oil to specied level.
Clean or change oil if necessary.
Replace with new one
Adjust relief valve setting with a
pressure gauge.
•
Retighten suction side piping
connections.
•
Add oil into oil tank.
•
Check pump oil seal.
Check hose or service strainer.
Retighten a loose joint.
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