JLG 3248RS/10RS Service Manual - Manual (Page 88)

SECTION 4 - HYDRAULICS
4-8 – JLG Lift – 3121273
4.7 CYLINDER REPAIR
NOTE: The following are general procedures that apply to the cylin-
ders on this machine. Procedures that apply to a specific cyl-
inder will be so noted.
Disassembly
NOTICE
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 port block fitting in the manifold located on the
cylinder.
DO NOT FULLY EXTEND CYLINDER TO THE END OF STROKE.
RETRACT CYLINDER SLIGHTLY TO AVOID TRAPPING PRESSURE.
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. Loosen the cylinder head set-
screw.
6. Using the proper wrench, loosen the cylinder head
and remove head from cylinder barrel.
When removing cylinder head do not force if binding
occurs. Reverse rotation a couple times and try
removing again. If still no release, tap barrel with
hammer in threaded area, and try again. Repeat if
necessary, until head is completely removed.
7. Attach a suitable pulling device to the cylinder rod
port block end or cylinder rod end, as applicable.
NOTICE
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.
8. With the barrel clamped securely, apply pressure to
the rod pulling device and carefully withdraw the
complete rod assembly from the cylinder barrel.
9. Using suitable protection, clamp the cylinder rod in
a vise or similar holding fixture as close to the piston
as possible.
NOTE: For steer cylinder piston removal, see Steer Cylinder Piston
Removal on page 4-9 following.
10. Loosen and remove the cap screw(s), if applicable,
which attach the tapered bushing to the piston.
11. Insert the cap screw(s) in the threaded holes in the
outer piece of the tapered bushing. Progressively
tighten the cap screw(s) until the bushing is loose
on the piston.
12. Remove the bushing from the piston.
13. Screw the piston CCW, by hand, and remove the
piston from cylinder rod.
14. Remove and discard the piston o-rings, seal rings,
and backup rings.
15. If applicable, remove the piston spacer from the rod.
16. Remove the rod from the holding fixture. Remove
the cylinder head gland and retainer plate, if applica-
Figure 4-3. Cylinder Barrel Support
Figure 4-4. Cylinder Rod Support