HYDRAULIC SYSTEM NBT40 SERVICE MANUAL
2-26 Published 8-01-2017 Control # 287-11
Boom will not extend
Cables not attached correctly. Reconnect, replace and/or adjust cables.
Anti-two block system shut down. Lower hook, and extend load.
Defective anti-two block system. Check anti-two block system; repair if defective.
Overload causing RCL shutdown.
Reduce load or radius until RCL resets and resume
operation.
Insufficient oil flow or pressure to extend
cylinder.
Check oil flow, repair if not to specification.
Turn pulsates for a few
seconds
Accelerating swing too rapidly.
Move joystick slowly and smoothly to start and stop
swing.
Turn pulsates continuously
and is slow
Low pilot circuit pressure.
Check and adjust pilot pressure to 3.45 MPa (500
PSI).
Turn will not start smoothly
or increases/decreases
speed drastically near full
joystick throw
Improper or defective valve spool springs or
burrs on valve spool.
Swing should start to rotate at 0.7 - 1 MPa (100 -
140 PSI) and be at full speed at 2.1 - 2.4 MPa (300 -
350 PSI). Check for free movement of spool in
valve body, hone spool if required. Replace spool
spring pack if necessary.
Turn moves erratically in
one quadrant
Machine out of level or windy conditions.
Level machine. Operate slowly and carefully in the
wind.
CONDITION POSSIBLE CAUSE POSSIBLE SOLUTION
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