National Crane Published 08/16/19 Control # 112-05 8-5
500E2 SERVICE MANUAL TROUBLESHOOTING
Systematic Troubleshooting
The following step-by-step analysis will be helpful in isolating
and correcting almost every service problem if followed in a
step by step systematic manner. Use this information with
the Hydraulic Schematic and the Illustrated Parts Catalog to
identify parts and flow paths. Start at the top box and work
downward step-by-step. Do not try to start in the middle or
skip steps.
JIB JACK TROUBLESHOOTING
Does not lift load
No oil in system
Release valve not closed
Add oil to reservoir tank through oil filler hole
Turn handle clockwise tightly
Lifts load only part way Oil level low Add oil to reservoir tank through oil filler hole
Lifts load but does not
hold
The following valve or valves leaking
a. Suction valve
b. Delivery valve
c. Release valve
Replace jack
Packings worn or damaged Replace jack
Jack does not lower
Release valve stuck, probably dirt or
foreign matter
Transfer load then replace dirty oil, flush oil
reservoir with kerosene
Poor lifting
Dirty oil
Air in hydraulic system
Change hydraulic oil
Purge air from system
Poor pumping action
Oil seal for pump unit worn out or
damaged
Replace jack
HYDRAULIC SYSTEM TROUBLESHOOTING CHART
Condition Possible Cause Possible Solution
Boom creeping down
Yes
No
Control valve in
meter in position.
Yes
No
Control Valve Centered
Cap sensing line between
the counterbalance valve
and the compensating
pressure switch.
Incorrect counterbalance
setting, bad counterbalance
valve, leaking cylinder seals
Replace compensating
pressure switch
Stops creep
Still creeps
Center valve
Control valve in
down position
normal operation
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