JLG 67SL Service Manual - Manual (Page 78)

SECTION 4 - HYDRAULICS
4-2 – JLG Lift – 3121322
4.3 CYLINDER CHECKING PROCEDURE
NOTE: Cylinder check must be performed anytime a system
component is replaced or when improper system
operation is suspected.
1. Using all applicable safety precautions, activate
engine and fully extend cylinder to be checked. Shut
down engine.
2. Carefully disconnect hydraulic hoses from retract
port of cylinder. There will be some initial weeping of
hydraulic fluid which can be caught in a suitable
container. After the initial discharge, there should be
no further drainage from the retract port.
3. Activate engine and extend cylinder.
4. If cylinder retract port leakage is less than 6-8 drops
per minute, carefully reconnect hose to port and
retract cylinder. If leakage continues at a rate of 6-8
drops per minute or more, cylinder repair must be
made.
5. With cylinder fully retracted, shut down engine and
carefully disconnect hydraulic hose from cylinder
extend port.
6. Activate engine and retract cylinder. Check extend
port for leakage.
7. If extend port leakage is less than 6-8 drops per
minute, carefully reconnect hose to extend port,
then activate cylinder through one complete cycle
and check for leaks. If leakage continues at a rate of
6-8 drops per minute or more, cylinder repairs must
be made.
4.4 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. Refer to
Figure 4-24. thru Figure 4-27. for specific cylinder
assembly breakdowns and for specific parts refer-
ences. Refer to JLG Parts Manual 3121323 for seal
kits and part numbers.
Disassembly
BEFORE REMOVING CYLINDERS FROM THE MACHINE BE SURE
TO SUPPORT THE MACHINE AND SCISSOR ARMS/PLATFORM
WITH SAFETY PROPS, FORKLIFTS, OR OVERHEAD CRANE TO
PREVENT RELEVANT COMPONENTS FROM COLLAPSING AND
CAUSING SERIOUS INJURY OR DEATH. (SEE FIGURE 4-28.)
1. Remove cylinder(s) from the machine by first dis-
connecting all hoses and/or wires and any valves.
Next, unscrew bolts connecting cylinder(s) to the
machine. If applicable, remove any pins connecting
the cylinders to the machine.
NOTE: Step 2 applies only to the Lift Cylinder.
2. To prevent damage, remove the hydraulic block,
load retaining valve block, and check valve block
from the lift cylinder barrel by unscrewing the 8 set
screws.
Cylinder
Barrel
Setscrews
Valve
Blocks
Figure 4-1. Lift Cylinder Valve Block Removal