JLG sky trak mmv Service Manual page 446

Hydraulic System
WARNING:
under pressure can penetrate the skin, causing
death or serious injury. Relieve hydraulic pres-
sure before servicing any hydraulic component.
4. Label or otherwise mark the hydraulic hoses (right
side) or tubes (left side) in relation to the slave
cylinder being removed. Disconnect and cap the
hydraulic hoses and slave cylinder fittings.
5. Securely support the slave cylinder. Remove the
nuts, capscrews and cylinder pins securing the slave
cylinder to the vehicle frame and outer boom.
6. With the help of at least one assistant, remove the
slave cylinder from the vehicle. Wipe up any
hydraulic fluid spillage in, on, near and around the
vehicle.
b. Slave Cylinder Disassembly
Note: An additional o-ring may be included at the base
of the cylinder rod. This additional o-ring may be dis-
carded, as it served only in a temporarily protective role.
1. Clean the slave cylinder (1) with a suitable cleaner
before inspection. Remove all dirt, debris and grease
from the cylinder.
IMPORTANT: Avoid using excess force when clamping
the cylinder in a vise. Apply only enough force to hold the
cylinder securely. Excessive force can damage the cylin-
der tube (2).
9.148
14
16
17
5
11
10
13
2
Escaping hydraulic fluid
15
4
1 9
8
7
6
19
2. Place the slave cylinder in a soft-jawed vise or other
acceptable holding equipment if possible.
3. Extend the rod (3) to allow access to the base of the
cylinder.
IMPORTANT: Protect the finish on the rod at all times.
Damage to the surface of the rod can cause seal failure.
4. Using a pin spanner wrench, unscrew the head
gland (4) from the tube (2). The head gland was
originally torqued at 250-300 lb/ft (339-407 Nm), so
a considerable amount of force is required to remove
it. 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
in the tube, prevent the threaded end of the tube from
damaging the piston (5). Keep the rod centered within
the tube to help prevent binding.
5. Carefully pull the rod (3) with all attachments straight
out of the tube (2).
6. Fasten the rod end 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. Remove the o-ring (6), back-up ring (7), locking
insert (8) and o-ring (9) from the head gland.
3
18
12
MT1940
Model MMV Rev. 12/04