JLG G6-42A Service Manual - Manual (Page 153)

8-25 G6-42A, G9-43A, G10-43A
Hydraulic System
Note: The extend/retract cylinder has a spacer that
MUST be installed over the rod
AFTER the head gland
and BEFORE the piston head.
3. 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.
Note: Protect the finish on the cylinder rod at all times.
Damage to the surface of the rod can cause seal failure.
4. Lubricate and slide the head gland over the cylinder
rod. Install the piston head on to the end of the
cylinder rod. Loctite
® 242™ and install the set screw
in the piston head. Refer to Section 8.8.4, “Cylinder
Torque Specifications—G6-42A” or Section 8.8.5,
“Cylinder Torque Specifications—G9-43A & G10-
43A” for torque specifications for the piston head
and the set screw.
Note: Avoid using excess force when clamping the
cylinder barrel in a vise. Apply only enough force to hold
the cylinder barrel securely. Excessive force can
damage the cylinder barrel.
5. Place the cylinder barrel in a soft-jawed vise or other
acceptable holding devise.
Note: When sliding the rod and piston assembly into the
cylinder barrel, prevent the threaded end of the cylinder
barrel from damaging the piston head. Keep the cylinder
rod centered within the barrel to prevent binding.
6. Carefully insert the cylinder rod assembly into the
cylinder barrel.
7. Screw the head gland into the cylinder barrel and
tighten with a spanner wrench. Refer to Section
8.8.4, “Cylinder Torque Specifications—G6-42A” or
Section 8.8.5, “Cylinder Torque Specifications—G9-
43A & G10-43A” for torque specifications for the
head gland.
8. If applicable, install new counter balance valve into
block on the cylinder barrel.
e. General Cylinder Installation
1. Grease the bushings at the ends of the hydraulic
cylinder. Using an appropriate sling, lift the cylinder
into it’s mounting position.
2. Align cylinder bushing and install pin, lock bolt or
retaining clip.
3. Connect the hydraulic hoses in relation to the labels
or markings made during removal.
4. Before starting the machine, check level of hydraulic
fluid in reservoir. Add hydraulic fluid if needed. Refer
to Section 8.5.2, “Hydraulic Oil Reservoir Filling.”
5. Start the machine and run at low idle for about one
minute. Slowly activate hydraulic cylinder function in
both directions allowing cylinder to fill with hydraulic
oil.
6. Inspect for leaks and check level of hydraulic fluid in
reservoir. Add hydraulic fluid if needed. Shut the
engine OFF.
7. Wipe up any hydraulic fluid spillage in, on, near and
around the machine, work area and tools.
8. Close and secure the engine cover.
8.8.2 Cylinder Pressure Checking
Attach a 5000 psi (345 bar) gauge to the test port on the
P1 port on the priority valve to check the system
pressure.
Note: If a hydraulic cylinder pressure is greater than the
main control valve pressure, increase the main control
valve pressure by adjusting the main relief. Generally,
one half turn clockwise will be adequate to check an
individual circuit. Activate the circuit and if pressure is
obtained turn the main relief counter clockwise one half
turn. Re-check the main relief setting and adjust if
necessary.
8.8.3 Steering Cylinders
The steer cylinder is attached to each axle center
housing.The steer cylinder assembly can be found in
Section 5.3, “Axle Specifications And Maintenance
Information.” The steer cylinder is covered in the
appropriate manufacturer’s axle literature.
AXLE CENTER SECTION
STEERING CYLINDER