Group 34, Uprights
34-2-4 • Troubleshooting SM 765, Nov ’06
• Gland static seals sealing surface damaged; check
grooves and bore.
Oil leak at top of lift cylinder
• Scored cylinder wall; see Section 5.
• Worn or damaged gland rod-seal; see procedures
for piston-type cylinders under “Cylinder leaking
internally.”
Unsatisfactory lift or tilt cylinder drift test results
• Cylinder leaking internally; remove cylinder gland
and check:
a. Primary cylinder should have only 3.4 ounces
(100 ml) on rod side of the piston
b. Piston-type lift and secondary cylinders should be
dry on rod side of piston.
If fluid is leaking past piston:
On piston-type cylinders, remove rod and piston,
clean check valves and clean and inspect/replace pis-
ton seals
See Section 5.
• Cylinder hydraulic fittings loose or worn; check
fitting O-rings, tighten fittings according to Group
40, “Hydraulic Fitting Tightening Procedure.”
• Check valve worn or damaged; remove rod and
piston, clean check valve and replace if necessary.
• Control valve spool linkage malfunctioning, dam-
aged, or worn; see Group 30, Section 5 for linkage
adjustment and/or replacement.
• Counterbalance function in main hydraulic control
valve malfunctioning, damaged, or worn; inspect
and clean or replace if necessary.
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