JLG sky trak mmv Service Manual page 456

Hydraulic System
11
13
d. Lift/Lower Cylinder Inspection
1. Inspect internal surfaces and all parts for wear,
damage, etc. If 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 (8) is straight. If it is bent, install a
new rod.
e. Lift/Lower Cylinder Assembly
Note: Follow Section 9.14.3, General Cylinder Assembly
Instructions.
1. Install a new oiled o-ring (22), back-up ring (21) and
o-ring (20) on the head gland (10).
9.158
1
26
24
23
19
16
15
28
17
18
14
10
9
8
10
12
25
21
22
12
27
3
5
4
2. Install the sealed outside diameter heavy-duty rod
wiper (25). The wiper lip (27) should be toward the
head gland. Install the deep Z-seal with back-up
(24), orienting the edge (28). Install the precision
wearbands (23) in the head gland. Use tools that will
not damage the seals.
3. Install the capped T-seal (17) and both precision
wearbands (16) on the piston (11).
Note: The T-seal actually consists of four components; a
wide, flexible inner band, the flexible T-seal band itself,
and two supportive split caps that mount on either side of
the "T" itself.
4. Install a new oiled o-ring (14) and back-up rings (15)
on the piston.
5. Install a new small oiled o-ring (18) into the
piston (11).
6. 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.
7. Carefully slide the head gland (10) onto the rod (8).
12
11
1
29
2
3
4
5
7
6
8
20
2
6
Model MMV Rev. 12/04
7 9
MT2801