JLG 120-SXJ ANSI Service Manual - Manual (Page 77)

SECTION 5 - HYDRAULICS
3121105 – JLG Lift – 5-5
5.4 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.
DO NOT FU LLY EXTEN D CYLINDER TO END OF STROKE.
RETRACT CYLINDER SLIGHTLY TO AVOID TRAPPING PRES-
SURE.
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.
FOR CYLINDERS WITH DOUBLE HOLDING VALVES, CRACK
BLEEDERS TO RELEASE PRESSURE BEFORE REMOVING HOLD-
ING VALVES.
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. Tap around outside of cylinder head retainer
with a suitable hammer to shatter loctite.
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
CYLINDER 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.
RO
D
S
U
P
P
O
RT
SUPPORT
TABLE
ROD CLAMP
PROTECTED
BARREL CLAMP
Figure 5-1. Cylinder Barrel Support
RO
D
S
U
P
P
O
RT
SUPPORT
TABLE SUPPORT
TABLE
ROD CLAMP
PROTECTED
Figure 5-2. Cylinder Rod Support