JLG 450A II Series, Service And Maintenance Manual

Page: 284 / 396

SECTION 5 - HYDRAULICS
5-44 – JLG Lift – 3121290
7. Using suitable protection, clamp cylinder rod in a vise or
similar holding fixture as close to piston as possible.
8. Loosen and remove cap screws attaching tapered bush-
ing to piston.
9. Insert cap screws in threaded holes in outer piece of
tapered bushing. Progressively tighten cap screws until
bushing is loose on piston.
10. Remove bushing from piston.
11. Screw piston counter-clockwise by hand and remove
from cylinder rod.
Figure 5-86. Tapered Bushing Removal
12. Remove and discard piston O-rings, seal rings, and
backup rings.
13. Remove piston spacer from rod.
14. 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 parts thoroughly with approved cleaning solvent.
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, scoring, and distor-
tion. 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, ovality, and tapering. Replace as needed.
13. Inspect rod and barrel bearings for excessive wear or
damage. Replace as necessary.
a. Clean hole, (steel bushing) of burrs, dirt, etc.
b. Inspect steel bushing for wear or damage. If steel
bushing is worn or damaged, rod/barrel must be
replaced.
c. Lubricate inside of steel bushing with WD40 before
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 5-87. 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 30 ft-lb (40Nm).
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.