JLG 450A_AJ Series II Service Manual - Manual (Page 260)

SECTION 5 - HYDRAULICS
5-20 – JLG Lift – 3121290
6. Using suitable protection, clamp cylinder rod in a vise or
similar holding fixture as close to piston as possible.
7. Loosen and remove cap screws attaching tapered bush-
ing to piston.
8. Insert cap screws in threaded holes in outer piece of
tapered bushing. Progressively tighten cap screws until
bushing is loose on piston.
9. Remove bushing from piston.
Figure 5-36. Tapered Bushing Removal
10. Screw piston counter-clockwise by hand and remove
piston from cylinder rod.
11. Remove and discard piston seals and lock rings.
12. Remove rod from holding fixture. Remove cylinder head
and ring washer. Discard 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 cylinder rod for scoring, tapering, ovality, or
other damage. Dress rod with Scotch Brite or equivalent
as needed. 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, scoring, and distor-
tion. Dress piston surface or replace piston as needed.
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 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 bearings for 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 before
installing composite bushings.
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 5-37. Composite Bushing Installation
14. Inspect oil ports for blockage or presence of dirt or other
foreign material. Repair as needed.
15. Inspect piston rings for cracks or other damage. Replace
as needed.