JLG 3246E2 Service Manual - Manual (Page 17)

SECTION 2 - PROCEDURES
3120855 – JLG Sizzor – 2-5
Cylinders w/Single Holding Valves - Lift
Cylinder
OPERATE ALL FUNCTIONS FROM GROUND CONTROL STATION
ONLY.
1. Using all applicable safety precautions, activate
hydraulic system.
WHEN WORKING ON THE LIFT CYLINDER, RAISE THE PLAT-
FORM COMPLETELY AND SUPPORT THE PLATFORM USING A
SUITABLE OVERHEAD LIFTING DEVICE.
DO NOT FULLY EXTEND LIFT CYLINDER TO END OF STROKE.
RETRACT CYLINDER SLIGHTLY TO AVOID TRAPPING PRES-
SURE.
2. Raise platform completely then retract cylinder
slightly to avoid trapping pressure. Place a suitable
overhead lifting device approximately 2.5 cm (1 in)
below the platform.
3. Shut down hydraulic system and allow machine to
sit for 10-15 minutes. Carefully remove hydraulic
hoses from cylinder port block.
4. There will be initial weeping of hydraulic fluid, which
can be caught in a suitable container. After the initial
discharge, there should not be any further leakage
from the ports. If leakage continues at a rate of 6-8
drops per minute or more, the holding valve is
defective and must be replaced.
5. If no repairs are necessary or when repairs have
been made, carefully reconnect hydraulic hoses to
the appropriate ports.
6. Remove lifting device from platform, activate hydrau-
lic system and run cylinder through one complete
cycle to check for leaks.
2.9 LIFT CYLINDER REMOVAL AND
INSTALLATION
Lift Cylinder Removal
1. Place the machine on a flat and level surface. Raise
the platform and attach a suitable lifting device to
the platform.
2. Remove the bolts and locknuts securing the cylinder
to the upper inner arm assembly. Drop the cylinder
out of the saddle on the inner arm assembly.
3. Retract the lift cylinder rod completely.
4. Tag and disconnect the hydraulic lines, then cap the
lift cylinder hydraulic lines and ports.
5. Remove the bolts and locknuts securing the barrel
end to the lower arm assembly.
6. Carefully remove the cylinder from the scissor lift
and place in a suitable work area.
Lift Cylinder Installation
1. Install lift cylinder in place using suitable slings,
aligning barrel end in lower arm assembly cylinder
saddle.
2. After the cylinder barrel is in place, Secure it with the
bolts and locknuts.
3. Remove cylinder port plugs and hydraulic line caps
and correctly attach lines to cylinder ports.
4. Extend the cylinder rod until the cylinder head aligns
with upper inside cylinder saddle. Set the head of
the cylinder in the saddle and replace the bolts and
locknuts.
5. Lower platform to stowed position and shut down
motor. Check hydraulic fluid level and adjust accord-
ingly.
2.10 LIFT CYLINDER REPAIR
Disassembly
DISASSEMBLY OF THE CYLINDER SHOULD BE PERFORMED ON
A CLEAN WORK SURFACE IN A DIRT FREE WORK AREA. BE
SURE TO CLEAN ALL DIRT OR OTHER FOREIGN SUBSTANCES
FROM CYLINDER OPENINGS - PARTICULARY AT THE HEAD.
1. Connect a suitable auxiliary hydraulic power source
to the cylinder port block fitting.
DO NOT FULLY EXTEND 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 nec-
essary
3. If applicable, remove the cartridge-type holding
valve and fittings from the cylinder port block. Dis-
card o-rings.