JLG 450A_AJ Series II Service Manual - Manual (Page 279)

SECTION 5 - HYDRAULICS
3121290 – JLG Lift – 5-39
7. Using suitable protection, clamp cylinder rod in a vise or
similar holding fixture as close to piston as possible.
8. Remove retainer from end of rod.
9. Remove nut, sleeve, and bushing.
10. Remove piston from rod.
11. Screw piston counter-clockwise by hand and remove
from cylinder rod.
12. Remove and discard piston O-rings, seal rings, and
backup rings.
13. Remove piston bushing from rod.
14. Remove rod from holding fixture.
15. Remove cylinder head. Discard O-rings, back-up rings,
rod seals, and wiper seals.
CLEANING AND INSPECTION
1. Clean all parts thoroughly with approved cleaning sol-
vent.
2. Inspect 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 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, ovality, and tapering. Replace as needed.
13. Inspect rod and barrel composite bushings for 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 the steel bushing with WD40
prior to bearing installation.
d. Using a correct size arbor, press bearing into steel
bushing.
NOTE: Lubrication is not required with nickel plated pins and
bearings. Install pin in composite bushing dry.
Figure 5-77. Composite Bushing Installation
14. Inspect travel limiting collar or spacer for burrs and
sharp edges. If necessary, dress inside diameter surface
with Scotch Brite or equivalent.
15. Inspect port block fittings and holding valves. Replace
as necessary. Torque valves to 51 ft-lb (70 Nm).
16. Inspect oil ports for blockage or presence of dirt or other
foreign material. Repair as necessary.
17. Inspect piston rings for cracks or other damage. Replace
as necessary.