Manitowoc National Crane NBT40 Series, Service Manual

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NBT40 SERVICE MANUAL HYDRAULIC SYSTEM
National Crane
Published 8-01-2017 Control # 287-11
2-25
Excessive noise during
operation
Low oil temperature. Allow unit to warm up.
Low hydraulic oil supply. Check and fill with crane in travel position.
Suction line kinked, collapsed or blocked. Clear blockage.
Hydraulic oil too thick. Warm oil or use oil more applicable to environment.
Plugged suction strainers. Remove from tank and clean.
Relief valve chattering. Dirt in relief valve or damaged relief.
Swing brake dragging. Bleed air from brake line at fitting on brake housing.
Hydraulic tubing vibration. Check for loose tubing.
Tank breather plugged. Clean breather.
Cylinders drift
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.
Hoist will not lift or hold
load
Load too heavy.
Check load and change to Lo-speed/Hi-pull or
applicable multipart reeving.
Hoist or boom overloaded causing RCL
shutdown. Reduce load or reeve hoist properly
forshutdown.load lifting.
Relief valve setting too low. Check and adjust if required.
Motor worn. Replace motor.
Sprag clutch defective. Clean or replace Sprag clutch.
Load block too close to boom tip, two-block
system shut down. Lower load or retract boom. Check two-block
system, repair if defective.
Brake worn out. Repair or replace brake.
Anti-two-block system defective. Repair anti-two-block system.
Hoist gearbox heats
Gearbox grease low. Check and fill as required.
Duty cycle too high. Reduce cycle time or speed of engine.
Truck engine will not start
from crane cab
Truck ignition switch on.
Turn truck ignition off.
Check all other normal motor vehicle systems as
outlined by normal practice.
Boom chatters during
extension/retraction or
doesn’t proportion properly
Boom sections need lubrication.
Use dry lubricant or replace lube plugs in wear
pads.
Wear pads not shimmed correctly. Reshim as described in boom assembly section.
Boom hot from high extend duty cycle. Slow duty cycle to cool boom and pads.
Worn wear pads. Replace pads.
Cylinder came out of lock. Disassemble and reinstall keepers.
Extension cables out of adjustment. Readjust cables and tension properly.
Extend or retract cables broken. Disassemble and inspect and replace cables.
CONDITION POSSIBLE CAUSE POSSIBLE SOLUTION
Reference Only