Cylinder Repair - JLG 3394RT Service Maintenance Manual

8. Place the 6 inch (15.2 cm) high block with ascension
ramp in front of right front wheel.
9. From platform control station, select LOW drive
speed.
10. Place DRIVE control switch to FORWARD position
and carefully drive the machine up ascension ramp
until right front wheel is on top of block.
11. Raise machine platform approximately 9 ft (2.7 m)
on the 3394RT or 10 ft (3.1 m) on the 4394RT.
12. Place DRIVE control switch to REVERSE position
and carefully drive the machine off the block and
ramp.
13. Have an assistant check to see that the right front
wheel remains locked in position off the ground.
14. Lower the machine platform; the lockout cylinder
should then release and allow wheel to rest on the
ground. It may be necessary to activate DRIVE to
release cylinders.
15. If the lockout cylinders do not function properly,
have qualified personnel correct the malfunction
prior to any further operation.
4.5

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
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 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.
3121133
3. If applicable, remove the cartridge-type holding
valve and fittings from the cylinder port block. Dis-
card o-rings.
Figure 4-1. Lift Cylinder Holding Valve and Fitting
4. Place the cylinder barrel into a suitable holding fix-
ture.
Figure 4-2. Cylinder Barrel Support
– JLG Lift –
SECTION 4 - HYDRAULICS
Removal
4-3