SECTION 4 - HYDRAULICS
3121642 – JLG Lift – 4-5
13. Remove the bushing from the piston.
14. Screw the piston counter-clockwise, by hand, and
remove the piston from cylinder rod.
15. Remove and discard the piston o-rings, seal rings, and
backup rings.
16. Remove piston spacer, if applicable, from the rod.
17. Remove the rod from the holding fixture. Remove the
cylinder head gland and retainer plate, if applicable. Dis-
card the o-rings, back-up rings, rod seals, and wiper
seals.
Cleaning and Inspection
1. Clean all parts thoroughly in an approved cleaning sol-
vent.
2. Inspect the cylinder rod for scoring, tapering, ovality, or
other damage. If necessary, dress rod with Scotch Brite
or equivalent. Replace rod if necessary.
3. Inspect threaded portion of rod for excessive damage.
Dress threads as necessary.
4. Inspect inner surface of cylinder barrel tube for scoring
or other damage. Check inside diameter for tapering or
ovality. Replace if necessary.
5. Inspect threaded portion of barrel for damage. Dress
threads as necessary.
6. Inspect piston surface for damage and scoring and for
distortion. Dress piston surface or replace piston as nec-
essary.
7. Inspect threaded portion of piston for damage. Dress
threads as necessary.
8. Inspect seal and o-ring grooves in piston for burrs and
sharp edges. Dress applicable surfaces as necessary.
9. Inspect cylinder head inside diameter for scoring or
other damage and for ovality and tapering. Replace as
necessary.
10. Inspect threaded portion of head for damage. Dress
threads as necessary.
11. Inspect seal and o-ring grooves in head for burrs and
sharp edges. Dress applicable surfaces as necessary.
12. Inspect cylinder head outside diameter for scoring or
other damage and ovality and tapering. Replace as nec-
essary.
13. If applicable, inspect rod and barrel bearings for signs of
correct excessive wear or damage. Replace as necessary.
a. Thoroughly clean hole, (steel bushing) of burrs, dirt
etc. to facilitate bearing installation.
b. Inspect steel bushing for wear or other damage. If
steel bushing is worn or damaged, rod/barrel must
be replaced.
c. Lubricate inside of steel bushing with WD40 prior to
bearing installation.
d. Using an arbor of the correct size, carefully press the
bearing into steel bushing.
NOTE: Install pin into the Gar-Max bearing dry. Lubrication is not
required with nickel plated pins and bearings.
14. Inspect travel limiting collar or spacer for burrs and
sharp edges. If necessary, dress inside diameter surface
with Scotch Brite or equivalent.
15. If applicable, inspect port block fittings and holding
valve. Replace as necessary.
16. Inspect the oil ports for blockage or the presence of dirt
or other foreign material. Repair as necessary.
17. If applicable, inspect piston rings for cracks or other
damage. Replace as necessary.
Assembly
NOTE: Prior to cylinder assembly, ensure that the proper cylinder
seal kit is used. See your JLG Parts Manual.
Figure 4-5. Tapered Bushing Removal
Figure 4-6. Bushing Installation
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