JLG 40H Service Manual - Manual (Page 30)

SECTION 2 - PROCEDURES
2-10
– JLG Lift – 3120240
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. Remove the set screw (s), if applicable, and nut
which attach the piston to the rod, and remove the
piston. Discard self-locking set screws.
10. Remove the piston rings.
11. Remove and discard the piston o-rings, seal rings,
and backup rings.
12. Remove the set screw, if applicable, piston spacer,
and wear ring, if applicable, from the rod.
13. Remove the rod from the holding fixture. Remove
the cylinder head gland and retainer, if applicable.
Discard the o-rings, back-up rings, rod seals, and
wiper seals.
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 excessive dam-
age. 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 seal and o-ring grooves in piston for burrs
and sharp edges. Dress applicable surfaces as nec-
essary.
8. Inspect cylinder head inside diameter for scoring or
other damage and for ovality and tapering. Replace
as necessary.
9. Inspect seal and o-ring grooves in head for burrs
and sharp edges. Dress applicable surfaces as nec-
essary.
10. If applicable, inspect cylinder head retainer or end
cap for surface or thread damage. Repair or replace
as necessary.
11. Inspect cylinder head outside diameter for scoring
or other damage and ovality and tapering. Replace
as necessary.
12. If applicable, inspect thread ring for scoring or other
damage. Dress threads or applicable surfaces as
necessary.
13. If applicable, inspect seal grooves in thread ring for
burrs and sharp edges. Dress applicable surfaces
as necessary.
14. If applicable, inspect rod and barrel bushings for
signs of correct lubrication and excessive wear.
Replace as necessary.
15. Inspect travel limiting collar or spacer for burrs and
sharp edges. If necessary, dress inside diameter
surface with Scotch Brite or equivalent.
16. If applicable, inspect port block fittings and holding
valve. Replace as necessary.
17. Inspect the oil ports for blockage or the presence of
dirt or other foreign material. Repair as necessary.
18. If applicable, inspect piston rings for cracks or other
damage. Replace as necessary.
NOTE: Steps (19) through (22) apply to the 3 Section Boom
telescope cylinder only.
19. Inspect chain sheave bushings for scoring, tapering,
ovality and for excessive wear and evidence of cor-
rect lubrication. Replace bushing as necessary.
20. Inspect sheave chain groove for damage. Replace
sheave assembly as necessary.
21. Inspect sheave attach pin for scoring or other dam-
age and for evidence of correct lubrication. Dress
pin surface with Scotch Brite or equivalent or
replace pin as necessary.
22. Inspect sheave pin lubrication drilling and fitting for
blockage or the presence of dirt or other foreign
material. Repair as necessary.
Assembly.
NOTE: Prior to cylinder assembly, ensure that the proper
cylinder seal kit is used. See your JLG Parts Manual.
Apply a light film of hydraulic oil to all components
prior to assembly.
WHEN INSTALLING ‘POLY-PAK’ PISTON SEALS, ENSURE SEALS
ARE INSTALLED PROPERLY. REFER TO FIGURE 2-3 FOR COR-
RECT SEAL ORIENTATION. IMPROPER SEAL INSTALLATION
COULD RESULT IN CYLINDER LEAKAGE AND IMPROPER CYLIN-
DER OPERATION.