JLG M4069 Service Manual - Manual (Page 79)

SECTION 4 - HYDRAULICS
3121639 – JLG Lift – 4-7
7. With the barrel clamped securely, apply pressure to
the rod pulling device and carefully withdraw the
complete rod assembly from the cylinder barrel.
8. Using suitable protection, clamp the cylinder rod in
a vise or similar holding fixture as close to the piston
as possible.
9. If applicable, loosen and remove the nut which
attaches the piston to the rod, then remove the pis-
ton from the rod.
10. If applicable, loosen and remove the cap screw(s)
securing the tapered bushing to the piston.
11. Insert the capscrew(s) in the threaded holes in the
outer piece of the tapered bushing. Progressively
tighten the cap screw(s) until the bushing is loose
on the piston, then remove the bushing from the pis-
ton.
12. Screw the piston counter-clockwise, by hand, and
remove the piston from the cylinder rod.
13. Remove and discard the piston o-rings, back-up
rings, guidelock rings and hydrolock seals.
14. If applicable, remove the piston spacer from the rod.
15. Remove the rod from the holding fixture. Remove
the cylinder head and retainer plate from the rod.
Cleaning and Inspection
1. Clean all parts thoroughly in an approved cleaning
solvent.
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 damage. Dress
threads as necessary.
4. Inspect inner surface of cylinder barrel tube for scor-
ing 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 necessary.
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 nec-
essary.
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 nec-
essary.
12. Inspect cylinder head outside diameter for scoring
or other damage and ovality and tapering. Replace
as necessary.
13. If applicable, inspect rod and barrel bearings for
signs of correct lubrication and excessive wear. If
necessary, replace bearings as follows:
a. Thoroughly clean steel bushing hole 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 or bar-
rel (as applicable) must be replaced.
c. Using arbor of the correct size, carefully press
the bearing into the steel bushing.
NOTE: Install the cylinder pin into the Garmax bearing dry.
Lubrication is not required with chrome 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.
Apply a light film of hydraulic oil to all components
prior to assembly.
GARMAX
BUSHING
Figure 4-4. Oil-lite Bearing Installation