JLG 150HAX Service Manual - Manual (Page 104)

SECTION 5 - HYDRAULICS
5-8 – JLG Lift – 3120817
5.5 CYLINDER REPAIR
NOTE: The following are general procedures that apply to
all of the cylinders on this machine. Procedures that
apply to a specific cylinder will be so noted.
Disassembly
DISASSEMBLY OF THE CYLINDER SHOULD BE PERFORMED ON A
CLEAN WORK SURFACE IN A DIRT FREE WORK AREA.
1. Connect a suitable auxiliary hydraulic power source
to the cylinder port block fitting.
2. Operate the hydraulic power source and extend the
cylinder. Shut down and disconnect the power
source. Adequately support the cylinder rod, if appli-
cable.
3. If applicable, remove the cartridge-type holding
valve and fittings from the cylinder port block. Dis-
card o-rings.
4. Place the cylinder barrel into a suitable holding fix-
ture.
5. Using a suitable spanner wrench, loosen the cylin-
der head retainer, if applicable, and/or cylinder head
gland, and remove from cylinder barrel.
6. Attach a suitable pulling device to the cylinder rod
port block end or cylinder rod end, as applicable.
EXTREME CARE SHOULD BE TAKEN WHEN REMOVING THE CYL-
INDER ROD, HEAD, AND PISTON. AVOID PULLING THE ROD OFF-
CENTER, WHICH COULD CAUSE DAMAGE TO THE PISTON AND
CYLINDER BARREL SURFACES.
7. With the barrel clamped securely, apply pressure to
the rod pulling device and carefully withdraw the
complete rod assembly from the cylinder barrel.
ONCE THE HEAD GLAND HAS CLEARED THE CYLINDER CASE
MOUTH, THE ROD MUST BE SUPPORTED CLOSE TO THE CYLIN-
DER CASE PRIOR TO THE PISTON BEING PULLED PAST THE CYL-
INDER CASE THREADS. THIS IS DONE TO AVOID DAMAGE TO THE
CYLINDER CASE THREADS, AND/OR THE PISTON AND PISTON
SEALS.
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 nylon point 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 rod and barrel bushings for
signs of correct lubrication and excessive wear.
Replace as necessary.