JLG 26MRT, Service & Maintenance

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SECTION 2 - PROCEDURES
3120791 – JLG Sizzor – 2-5
Cylinders w/Single Counterbalance 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 1 inch (2.5
cm) 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 counterbalance 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
Removal
1. Place the machine on a flat and level surface. Start
the motor and raise the platform. Shut down the
engine and attach a suitable lifting device to the plat-
form.
2. Remove the bolt and locknut securing the cylinder
rod attach pin to the upper inner arm assembly.
Using a suitable brass drift, drive out the rod end
attach pin from the 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 bolt and locknut securing the barrel end
attach pin to the lower arm assembly. Using a suit-
able brass drift, drive out the barrel end attach pin
from the arm assembly.
6. Carefully remove the cylinder from the scissor lift
and place in a suitable work area.
Installation
1. Install lift cylinder in place using suitable slings,
aligning barrel end attach 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 the
bolt and locknut.
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 hole with the hole in arm assembly.
Secure the pin in place with the bolt and locknut.
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.
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 nec-
essary.