2-2 Published 08/16/19 Control # 112-05
HYDRAULIC SYSTEM 500E2 SERVICE MANUAL
• Park the crane it causes the least interference with other
equipment or operations in the area.
• Place all controls at the off position and secure all
operating features from inadvertent motion by brakes or
other means.
• Disable all methods used to start the truck's engine.
• Power plant stopped or disconnected at take-off.
• Boom lowered to the ground or otherwise secured
against dropping.
• Load block lowered to ground or otherwise secured
against dropping.
• Relieve hydraulic oil pressure from all hydraulic circuits
before loosening or removing hydraulic components.
After adjustments and repairs have been made, the crane
shall not be returned to service until all guards have been
reinstalled, trapped air removed from hydraulic system if
required, safety devices reactivated, and maintenance
equipment and all warning tags removed.
Adjustments and repairs shall be done only by designated
personnel who are properly trained. Use only National Crane
supplied parts to repair the crane.
Hydraulic System Maintenance Precautions
Contaminants in a hydraulic system affect operation and can
result in serious damage to the system components. If
evidence of foreign particles is found in the hydraulic system,
flush the system.
Disassemble and assemble hydraulic components on a
clean surface. Clean all metal parts in a nonflammable
cleaning fluid. Lubricate all components to aid in assembly.
Inspect all sealing elements (O-ring, gaskets, etc.) when
disassembling and assembling the hydraulic system
components. Installation of new sealing elements is always
recommended.
When installing metal hydraulic tubes, tighten all bolts finger
tight. Then, in order, tighten the bolts at the rigid end, the
adjustable end, and the mounting brackets. After tubes are
mounted, install the hoses. Connect both ends of the hose
with all bolts finger tight. Position the hose so it does not rub
the machine or another hose and has a minimum of bending
and twisting. Tighten bolts in both couplings.
Due to manufacturing methods, there is a natural curvature
to a hydraulic hose. The hose should be installed so any
bend is with this curvature.
In case of replacement hoses with angled stem reusable
fittings, the hose curvature must be taken into consideration
when assembling and positioning the angled stem.
Label Parts When Disassembling
When removing or disconnecting a group of wires or cables,
tag each one to ensure proper identification during re-
assembly.
When shims are removed, tie them together and identify
them as to location. Keep shims clean and flat until they are
reinstalled.
Welding Precautions
Sensitive truck computer system and crane's jib load limiting
device computer system components may be damaged by
welding on the truck or crane. The following precautions
should be taken:
• Disconnect truck battery cables (positive and negative)
• Attach welding ground lead as close as possible to area
to be welded.
• Remove the jib from the crane before welding on the
crane or remove the jib sheave case assembly from the
jib before welding on the jib.
Hydraulic Oil Recommendations
For the hydraulic oil specifications, Reference Lubrication,
page 7-1.
Draining and Flushing
If a component has been changed because of a failure that
might allow metal or abrasive particles to enter the system,
all systems must be thoroughly checked, drained, and
flushed.
1. Remove the reservoir drain plug. Allow about three
minutes after hydraulic oil stops flowing from the drain
port for the side walls to drain.
2. Clean and install the reservoir plug and fill the reservoir
with a 50/50 mixture of fuel oil and clean hydraulic oil.
3. Cycle the crane through all functions several times.
Then return the crane to its stowed position and turn the
front and rear wheels to the extreme left. Shut down the
engine.
4. Remove the reservoir drain plug and drain the reservoir.
Clean and install the drain plug and fill the reservoir with
clean hydraulic oil.
NOTE: Hydraulic oil supply lines must be connected to the
cylinders when flushing the system.
Draining the various components will be aided by
connecting a drain line in place of the disconnected
return line.
5. Disconnect the return line from the lift cylinder and raise
the boom to maximum elevation.
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