JLG G6-23A Service Manual - Manual (Page 87)

8.17 G5-19A, G6-23A
Hydraulic System
Note: It may be necessary to apply heat to break the
bond of the sealant between the piston and the rod
before the piston can be removed.
Some cylinder parts are sealed with a special organic
sealant and locking compound. Before attempting to
disassemble these parts, remove any accessible seals
from the area of the bonded parts. Wipe off any hydraulic
oil, then heat the part(s) uniformly to break the bond. A
temperature of 300-400° F (149-204° C) will destroy the
bond. Avoid overheating, or the parts may become
distorted or damaged. Apply sufficient torque for removal
while the parts are still hot. The sealant often leaves a
white, powdery residue on threads and other parts, which
must be removed by brushing with a soft brass wire brush
prior to reassembly.
9. Remove the piston head (4) from the rod (5) and
carefully slide the head gland (6) off the end of the
rod.
10. Remove all seals, back-up rings and o-rings (2) from
the piston head and all seals, back-up rings and o-
rings from the head gland.
Note: The head gland bearing will need to be inspected
to determine if replacement is necessary.
DO NOT attempt to salvage cylinder seals, sealing rings
or o-rings. ALWAYS use a new, complete seal kit when
rebuilding hydraulic components. Consult the parts
manual for ordering information.
8.11.3 Cylinder Cleaning Instructions
1. Discard all seals, back-up rings and o-rings. Replace
with new items from complete seal kits to help
ensure proper cylinder function.
2. Clean all metal parts with an approved cleaning
solvent such as trichlorethylene. Carefully clean
cavities, grooves, threads, etc.
Note: If a white powdery residue is present on threads
and parts, it can be removed. Clean the residue away
with a soft brass wire brush prior to reassembly, and
wipe with loctite
® cleaner before reinstallation.
8.11.4 Cylinder Inspection
1. Inspect internal surfaces and all parts for wear,
damage, etc. If the inner surface of the tube does not
display a smooth finish, or is scored or damaged in
any way, replace the tube.
2. Remove light scratches on the piston, rod or inner
surface of the tube with a 400-600 grit emery cloth.
Use the emery cloth in a rotary motion to polish out
and blend the scratch(es) into the surrounding
surface.
3. Check the piston rod assembly for run-out. If the rod
is bent, it must be replaced.
8.11.5 General Cylinder Assembly
1. Use the proper tools for specific installation tasks.
Clean tools are required for assembly.
2. Install new seals, back-up rings and o-rings (2) on
the piston (4) and the head gland (6).
Note: The Crowd cylinder has a spacer that MUST be
installed over the rod AFTER the head gland and
BEFORE the piston head.
3. Fasten the rod eye in a soft-jawed vise, and place a
padded support under and near the threaded end of
the rod (5) to prevent any damage to the rod.
IMPORTANT: Protect the finish on the rod at all times.
Damage to the surface of the rod can cause seal failure.
4. Lubricate and slide the head gland (6) over the
cylinder rod (5). Install the piston head (4) on to the
end of the cylinder rod. Loctite
® and install the
setscrew (3) in the piston head. Refer to Section
8.11.8, “Hydraulic Cylinder Torque Specifications,”
for tightening guidelines for the piston head and the
set screw.
IMPORTANT: Avoid using excessive force when
clamping the cylinder barrel in a vise. Apply only enough
force to hold the cylinder barrel securely. Excessive force
can damage the cylinder barrel.
5. Place the cylinder barrel (1) in a soft-jawed vise or
other acceptable holding equipment if possible.
IMPORTANT: When sliding the rod and piston assembly
into the cylinder barrel, prevent the threaded end of the
cylinder barrel from damaging the piston head. Keep the
cylinder rod centered within the barrel to prevent binding.
6. Carefully insert the cylinder rod assembly into the
tube.
7. Screw the head gland (6) into the cylinder barrel (1)
and tighten with a spanner wrench. Refer to Section
8.11.8, “Hydraulic Cylinder Torque Specifications,”
for tightening guidelines for the head gland.
8. If applicable, thread the new counterbalance valve
into the block on the cylinder barrel.