JLG 740AJ, Service And Maintenance Manual

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SECTION 5 - BASIC HYDRAULIC INFOR M ATION AND SCHE M ATICS
3121160 5-7
5.6 CYLINDER REPAIR
Upright Level Cylinder
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 FULLY EXTEND CYLINDER TO THE END OF STROKE. RETRACT CYLINDER
SLIGHTLY TO AVOID TRAPPING PRESSURE.
2. Operate the hydraulic power source and extend the cyl-
inder. Shut down and disconnect the power source.
Adequately support the cylinder rod, if applicable.
3. Remove the counterbalance holding valves and plugs
from the cylinder port block. Discard o-rings.
4. Place the cylinder barrel into a suitable holding fixture.
5. Mark cylinder head and barrel with a center punch for
easy realignment. Using an allen wrench, loosen the cyl-
inder head retainer capscrews and remove capscrews
from cylinder barrel.
6. Attach a suitable pulling device to the cylinder rod port
block end or cylinder rod end, as applicable.
EXTREME CARE SHOULD BE TAKEN WHEN REMOVING THE C YLINDER ROD,
HEAD, AND PISTON. AVOID PULLING THE ROD OFF-CENTER, WHICH COULD
CAUSE DAMAGE TO THE PISTON AND CYLINDER BARREL SURFACES.
7. With the barrel clamped securely, apply pressure to the
rod pulling device and carefully withdraw the complete
rod assembly from the cylinder barrel.
ROD SUPPORT
PROTECTED ROD CLAMP
BARREL CLAMP
SUPPORT TABLE
Figure 5-1. Cylinder Barrel Support
CAPSCREW
BARREL
PUNCH MARK
CYLINDER HEAD
WASHER
RING
Figure 5-2. Capscrew Removal
SUPPORT TABLE
ROD SUPPORT
Figure 5-3. Cylinder Rod Support