JLG M4069 Service Manual - Manual (Page 78)

SECTION 4 - HYDRAULICS
4-6 – JLG Lift – 3121639
Lift Cylinder Installation
1. Install lift cylinder in place using a suitable slings,
aligning barrel end attaching pin mounting holes on
lower arm assembly.
2. Using a suitable drift, drive the barrel end attach pin
through the mounting holes in the lift cylinder and
the lower arm assembly. Secure in place with bolt,
locknut and keeper shaft.
3. Remove cylinder port plugs and hydraulic line caps
and correctly attach lines to cylinder ports.
4. Extend the cylinder rod until the attach pin hole
aligns with those in the upper arm assembly. Using a
suitable drift, drive the cylinder rod attach pin
through the aligned holes, taking care to align the
pin retaining holes with the hole on the arm assem-
bly. Secure the pin in place with bolt, locknut and
keeper shaft.
5. Lower platform to stowed position and shut down
motor. Check hydraulic fluid level and adjust accord-
ingly.
NOTE: Always check hydraulic fluid level after completely
elevating and lowering machine.
4.11 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. Operate the hydraulic power source and extend the
cylinder. Shut down and disconnect the power
source. Adequately support the cylinder rod, if nec-
essary.
2. If applicable, remove the cartridge-type holding
valve and fittings from the cylinder port block. Dis-
card o-rings.
3. Place the cylinder barrel into a suitable holding fix-
ture.
4. To aid in realignment, mark cylinder head and barrel
with a center punch.
5. Using a suitable spanner wrench, loosen the span-
ner nut retainer and remove the spanner nut from
the cylinder barrel.
6. Attach a suitable pulling device to the cylinder rod
port block 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.
Figure 4-1. Barrel Support
Figure 4-2. Cap Screw Removal
Figure 4-3. Rod Support