National Crane 600H, Service Manual

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2
NATIONAL CRANE
08-19-2022 Control # 092-13
2-13
600H SERVICE MANUAL HYDRAULIC SYSTEM
Swing moves erratic or
loosely (Standard
system)
Loose turntable bearing. Torque bearing mounting bolts.
Loose swing gearbox mounting bolts. Tighten bolts.
Worn gears or bearing. Replace worn parts or adjust gearbox spacing.
Operator control of lever too erratic. Operate controls smoothly.
Motor counterbalance valves dirty or not
set properly. Clean or replace counterbalance valves not set at
600 psi.
Brake not holding properly.
Replace worn brake parts or shim brake to proper
torque.
Replace worn brake parts or shim brake to proper
torque
Brake releasing at wrong time or erratically.
Bleed air from brake with bleed screw on side of
brake.
Swing speed adjustment set too low. Adjust valve on turn motor.
Swing will not turn
(Standard System)
Turn circuit relief valves sticking. Clean and check circuit pressure.
Turntable bearing drag. Lubricate thoroughly as rotating boom.
Brake not releasing properly.
Check for 200 + PSI brake pilot pressure. Clean pilot
line or adjust motor counterbalance valves.
Adjust or clean brake for proper release.
Swing speed adjustment set too low. Adjust valve on turn motor.
Excessive pump noise
during operation
Excessive pump speed. Adjust foot throttle or check for too high PTO ratio.
Low oil temperature. Allow unit to warm up.
Low hydraulic oil supply. Check and fill.
Suction line kinked, collapsed or blocked. Clear blockage.
Pump Cavitation Check for loose clamps.
Hydraulic oil too thick. Warm oil or use oil more applicable to environment.
Relief valve chattering. Dirt in relief valve or damaged relief.
Hydraulic tubing vibration. Check for loose tubing.
Tank breather plugged. Clean breather.
Cylinders drift
Not getting oil to cylinders. Clean and replace as required.
Worn or damaged piston seals. Replace as required.
Air in hydraulic oil. Cycle operate crane cylinder to remove air.
Loose holding valve. Tighten valve.
Dirt in holding or check valve. Clean valve.
HYDRAULIC SYSTEM TROUBLESHOOTING CHART
Condition Possible Cause Possible Solution
REFERENCE ONLY