JLG 4017PS Service Manual - Manual (Page 152)

Hydraulic System
8-20 3706PS, 3707PS, 4014PS, 4017PS, 33.7, 37.6, 37.7
d. Steering Test
Refer to Section 8.5.1, “Hydraulic Pressures.”
1. Conduct a pressure check of the steering hydraulic
circuit.
2. Check each steering mode for proper function.
8.11 HYDRAULIC CYLINDERS
8.11.1 General Cylinder Removal
Instructions
1. Remove any attachment from the machine. Park the
machine on a firm level surface and fully retract the
boom. Allow sufficient work space around the
hydraulic cylinder being removed. Support the boom
if the lift/lower cylinder is being removed. Place the
travel select lever in (N) NEUTRAL, engage the park
brake, shut the engine OFF and chock wheels.
2. Place a Do Not Operate Tag on both the ignition key
switch and the steering wheel.
3. Open the engine cover. Allow the system fluids to
cool.
4. Label, disconnect and cap or plug hydraulic hoses in
relation to the cylinder.
5. Attach a suitable sling to an appropriate lifting device
and to the cylinder. Make sure the device used can
actually support the cylinder.
6. Remove the lock bolt and/or any retaining clips
securing the cylinder pins. Remove the cylinder pins.
7. Remove the cylinder.
8. Wipe up any hydraulic fluid spillage in, on, near and
around the machine, work area and tools.
a. General Cylinder Disassembly
1. Clean the cylinder with a suitable cleaner before
disassembly. Remove all dirt, debris and grease
from the cylinder.
2. Clamp the barrel end of the cylinder in a soft-jawed
vise or other acceptable holding equipment if
possible.
Note: Avoid using excessive force when clamping the
cylinder in a vise. Apply only enough force to hold the
cylinder securely. Excessive force can damage the
cylinder tube.
3. If applicable, remove the counterbalance valve from
the side of the cylinder barrel.
Note: DO NOT tamper with or attempt to adjust the
counterbalance valve cartridge. If adjustment or
replacement is necessary, replace the counterbalance
valve with a new part.
4. Extend the rod as required to allow access to the
base of the cylinder.
Note: Protect the finish of the rod at all times. Damage
to the surface of the rod can cause seal failure.
5. Using a pin spanner wrench, unscrew the head
gland from the tube. A considerable amount of force
will be needed to remove the head gland. Carefully
slide the head gland down along the rod toward the
rod eye, away from the cylinder barrel.
Note: When sliding the rod and piston assembly out of
the barrel, prevent the threaded end of the barrel from
damaging the piston. Keep the rod centered within the
barrel to help prevent binding.
6. Carefully pull the rod assembly along with the head
gland out of the cylinder barrel.
7. Fasten the rod eye in a soft-jawed vise, and place a
padded support under and near the threaded end of
the rod to prevent any damage to the rod.
8. Remove the set screw from the piston head.
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.
MZ0400
WARNING
Significant pressure may be trapped inside the cylinder.
Exercise caution when removing a counterbalance valve
or a pilot-operated check valve from a cylinder.