JLG 600SC_660SJC Service Manual - Manual (Page 89)

SECTION 5 - HYDRAULICS
3120898 – JLG Lift – 5-3
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
IMPORTANT
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 FULLY EXTEND CYLINDER TO THE 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.
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. Mark cylinder head and barrel with a center punch
for easy realignment. Using an allen wrench, loosen
the eight (8) cylinder head retainer cap screws, and
remove cap screws from cylinder barrel.
6. Attach a suitable pulling device to the cylinder rod
port block end or cylinder rod end, as applicable.
IMPORTANT
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.
8. Using suitable protection, clamp the cylinder rod in
a vise or similar holding fixture as close to the piston
as possible.
Figure 5-1. Cylinder Barrel Support
Figure 5-2. Cap Screw Removal
Figure 5-3. Cylinder Rod Support