JLG 450A_AJ Series II Service Manual - Manual (Page 274)

SECTION 5 - HYDRAULICS
5-34 – JLG Lift – 3121290
1. Using suitable protection, clamp cylinder rod in a vise or
similar holding fixture as close to piston as possible.
2. Loosen and remove cap screws attaching tapered bush-
ing to piston.
3. Insert cap screws in threaded holes in outer piece of
tapered bushing. Progressively tighten cap screws until
bushing is loose on piston.
4. Remove bushing from piston.
5. Screw piston counter-clockwise. Remove from cylinder
rod.
Figure 5-64. Tapered Bushing Removal
6. Remove and discard piston O-rings, seal rings, and
backup rings.
7. Remove piston spacer from rod.
8. Remove rod from holding fixture. Remove cylinder head
gland and retainer plate, if applicable. 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 for damage, scoring, and 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 surfaces as necessary.
9. Inspect cylinder head inside diameter for scoring or
other damage, ovality, and tapering. Replace as needed.
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
needed.
13. Inspect rod and barrel bearings for excessive wear or
damage. Replace as needed.
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. Press bearing in bushing using correct size arbor.
NOTE: Lubrication is not required with nickel plated pins and
bearings. Install pin in composite bushing dry.
Figure 5-65. 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 needed. Torque valves 50-55 ft-lb (68-75 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 needed.