JLG 1500SJ Service Manual - Manual (Page 398)

SECTION 5 - HYDRAULICS
5-46 – JLG Lift – 3121262
Jib Telescope Cylinder
USE CARE IN REMOVAL OF ANY, AND ALL, COMPONENTS AS
COUNTERBALANCE VALVES MAY RETAIN CONSIDERABLE PRES-
SURE WITHIN THE CYLINDER ASSEMBLY. USE EXTREME CARE
REMOVING PLUGS, VALVES, AND/OR THE ROD ASSEMBLY TO
ENSURE THE INTERNAL CYLINDER PRESSURE HAS BEEN
RELIEVED.
NOTE: The jib telescope cylinder weighs approximately
130.5 lbs. (59.2 kg).
DISASSEMBLY
1. Retract cylinder and support equipment to allow for
cylinder removal. Relieve system pressure to the cyl-
inder. Clean any debris from around both ports and
remove the hydraulic lines. Plug/cap both ports and
remove cylinder from equipment.
2. The cylinder assembly should be secured in such a
way as to prevent movement of the barrel assembly
while removing the rod assembly. (Such as in a vise
with pipe jaws.) Caution should be used to avoid
damaging the rod surface and to avoid excessive
deformation of the barrel, which could permanently
damage the unit. Provisions must also be made to
support the rod assembly during its removal.
3. Remove all dirt, grease, and other contaminants
from around the ports and the head gland. Drain all
oil from the unit. Extending and retracting the rod
manually can help purge the bulk of remaining oil.
4. Mark the orientation of the rod, gland, pad support,
and barrel with a permanent marker or paint pen. Do
not paint the chromed surface of the rod! Remove
the cap screws retaining the head gland from the
cylinder assembly.
NOTE: The threads are “locked” with a non-permanent
thread adhesive during assembly; a quick tug on the
wrench may be necessary to release the thread
adhesive.
5. Remove the rod assembly from the barrel using care
not to damage the threads or any other components
surface.
6. Clamp the rod mount and support the rod assembly
with the chrome surface protected. Remove the pis-
ton assembly by unthreading the piston itself from
the rod using a spanner wrench.
INSPECTION
1. Inspect all seals, backup rings, wipers, and wear
rings for tears, grooves, foreign matter, and exces-
sive wear. Deep grooves may be an indication of
damage to the barrel bore, rod chrome, or the pres-
ence of large particle contamination.
2. Remove the seals, backup rings, wipers, and wear
rings using a soft metal tool (brass or aluminum)
with rounded edges. Use care not to nick or score
the surfaces of any component, especially the seal
grooves.
3. Wipe all components clean with a lint-free cloth.
Plug the barrel opening with a lint-free cloth.
Remove any adhesive remnants from the head
gland, barrel, rod, and piston threads (where appli-
cable) using a soft wire brush. Use care not to
scratch or otherwise damage the critical surfaces of
any component including seal grooves, barrel bore,
rod chrome, etc.
4. Inspect the piston and head gland for excessive
wear, cracks, scoring, or any other damage. If wear
is present on the O.D. of the piston or the I.D. of the
head gland, check to ensure that the circularity of
both dimensions are within 0.007”. Beyond this limit
the seal performance is compromised and the com-
ponents must be replaced.
5. The stop tube should be inspected for cracking and
excessive flaring of the ends.
6. Closely inspect the chrome surface of the rod. Any
nicks, gouges, or scratches that penetrate the
chrome plating or result in a sharp edge, which may
damage seals, are cause for rod assembly replace-
ment.
7. Flush the barrel and fluid tube (if equipped), drain,
and wipe dry with a lint-free cloth. Closely inspect
bore for nicks, gouges, or scratches. Replace barrel
assembly if any of these are present.