SkyTrak 8042 Service Manual User Manual
Page 540
8.125
Model 8042, 10042, 10054 Legacy
Rev. 10/03
Hydraulic System
5. Using a pin spanner wrench, unscrew the head
gland (6) from the tube (2). The head gland was
originally torqued to 300-400 lb-ft (407-542 Nm), so
a considerable amount of force is required. Carefully
slide the head gland down along the rod toward the
eyelet end, away from the cylinder tube (2).
IMPORTANT: When sliding the rod and piston assembly
out of the tube, prevent the threaded end of the tube
from damaging the piston (7). Keep the rod centered
within the tube to help prevent binding.
6. Carefully pull the rod (5) with all attachments straight
out of the tube (2).
7. Fasten the rear of the rod in a soft-jawed vise, and
put a padded support below and near the threaded
end of the rod to help prevent damage to the rod.
8. Remove the setscrews (12 and 13) from the piston
(7). The setscrews are used to provide a secondary
lock on the piston. Pry or drill out the setscrews as
required. DO NOT damage the piston threads. New
setscrews will be required for reassembly.
9. Remove the precision wearbands (14), the piston
seal (15) and the square ring (16) from the piston.
10. Remove the piston (7) from the rod (5). The piston
was installed with Loctite #271 and torqued to 1800-
2000 lb-ft (2441-2712 Nm).
Note: It may be necessary to apply heat to break the
bond of the sealant between piston (7) and the rod (5)
before the piston can be removed. Some parts of
cylinders 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 joint.
Wipe off any hydraulic oil and heat the joint 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 or
pressure for removal while the parts are still hot.
Breakdown of sealant will leave a white, powdery
residue on threads and parts. Clean the residue away
with a soft brass wire brush prior to reassembly, and
wipe with Loctite “T” cleaner before reinstallation.
11. Remove the rod spacer (17).
12. From within the piston (7), remove the back-up ring
13. Remove the o-ring (8), back-up ring (9), locking
insert (10) and o-ring (11) from the head gland (6).
Remove them from the rod (5).
14. Remove the head gland (6) from the rod (5).
15. From within the head gland (6), remove the precision
wearbands (20) and, if installed, the buffer seal (21).
Remove the sealed outside diameter heavy-duty rod
wiper (22), the U-cup seal (23) and the o-ring (24).
c. Extend/Retract Cylinder Cleaning
1. Remove all hydraulic fluid, dirt and debris from the
inner surface of the cylinder tube (2).
2. Discard all seals, back-up rings, o-rings, etc.
Replace with new items from complete seal kits (25
and 26) to help ensure proper cylinder function.
3. 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 “T” cleaner before reinstallation.
d. Extend/Retract Cylinder Inspection
1. Inspect internal surfaces and all parts for wear,
damage, etc. If the inner surface of the tube (2) does
not display a smooth finish, or is scored or damaged
in any way, replace the tube. Often, dirty hydraulic
fluid causes failure of internal seals and damage to
the smooth surface within the tube.
2. Remove slight scratches on the piston, rod or inner
surface of the tube with very fine grit emery cloth.
Use the emery cloth in a rotary motion to polish out
and blend the scratch(es) into the surrounding
surface.
3. Clean parts with trichlorethylene.
4. Check that the rod (5) is straight. If it is bent, install a
new rod.