5-1
The information supplied in this section of the
manual is designed to assist you in service and repair
of your National Crane. Inspection, lubrication and gen-
eral maintenance information are found in two previous
sections of this manual. Before attempting to perform
any service work, the machine must be shut down as
outlined under “Adustments and Repairs” in the Mainte-
nance section of this book.
Generally, a study of the hydraulic schematics in
conjunction with a systematic procedure to locate and
correct the problem will enable a skilled mechanic to
determine the problem and correct it. If at any time you
cannot find or correct the problem, contact your local
distributor or National Crane Product Support Depart-
ment.
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This information is on the serial number placard
located on the crane frame.
The following general suggestions should be help-
ful in analyzing and servicing your crane. Use the fol-
lowing systematic approach should be helpful in finding
and fixing problems:
1. Determine the problem.
2. List possible causes.
3. Devise checks.
4. Conduct checks in a logical order to determine
the cause.
5. Consider the remaining service life of compo-
nents against the cost of parts and labor neces-
sary to replace them.
6. Make the necessary repair.
7. Recheck to ensure that nothing has been over-
looked.
8. Functionally test the new part in its system.
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An important item in preserving the long life of the
crane is keeping dirt out of working parts. Enclosed
compartments, seals, and filters have been provided to
keep the supply of air, fuel and lubricants clean. It is
important that these enclosures be maintained.
Whenever hydraulic, fuel, lubricating oil lines are dis-
connected, clean the adjacent area as well as the point
of disconnect. As soon as the disconnection is made,
cap, plug or tape each line or opening to prevent entry
of foreign material. The same recommendation for clean-
ing and covering apply when access covers or inspec-
tion plates are removed.
Clean and inspect all parts. Be sure all passages
and holes are open. Cover all parts to keep them clean.
Be sure parts are clean when they are installed. Leave
new parts in their containers until ready for assembly.
+ !
Contaminants in a hydraulic system affect opera-
tion and will result in serious damage to the system com-
ponents. Dirty hydraulic systems are a major cause of
component failures.
If evidence of foreign particles is found in the hy-
draulic system, flush the system.
Disassemble and assemble hydraulic components
on a clean surface.
Clean all metal parts in a nonflammable cleaning
fluid. Then lubricate all components to aid in assembly.
Inspect all sealing elements (O-ring, gaskets, etc.)
when disassembling and assembling the hydraulic sys-
tem 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 brack-
ets. After tubes are mounted, install the hoses. Con-
nect both ends of the hose with all bolts finger tight.
Position the hose so it does not rub the machine or an-
other 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 in-
stalled so any bend is with this curvature.
In case of replacement hoses with angled stem re-
usable fittings, the hose curvature must be taken into
consideration when assembling and positioning the
angled stem.
Reference Only
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