JLG G6-42A Service Manual - Manual (Page 157)

8-23 G6-42A, G9-43A, G10-43A
Hydraulic System
2. Remove the plastic cap from the brake bleeder (2).
Attach one end of a length of transparent tubing over
the brake bleeder. Place the other end of this tubing
in a suitable transparent container that is partially
filled with hydraulic oil. The end of the tubing must
be below the oil level in the container.
3. DO NOT open the brake bleeder without holding the
tubing firmly on the bleeder. There is pressure at the
brakes. Carefully open the bleeder with a 12mm
wrench. Have the assistant depress the brake pedal.
Close the brake bleeder when air bubbles no longer
appear in the oil. Release the brake pedal. Remove
the tubing from the brake bleeder.
4. Repeat Steps 2 and 3 for the remaining brake
bleeders.
5. Install a vacuum pump on the brake reservoir and
remove the remainder of the trapped air from the
brake system.
6. Check brake fluid level and add fluid if necessary.
7. Conduct a pressure and function check of the
service brake. Refer to Section 8.4.1, “Hydraulic
Pressures.”
8.7.4 Steering Orbitrol Valve
The steering orbitrol valve (3) is located at the base of the
steering wheel shaft, concealed by the lower dash cover.
The valve is not serviceable and must be replaced in its
entirety if defective. For detailed information refer to
Section 4.3.1, “Steering Column and Orbitrol Valve.”
8.7.5 Steer Select Valve
The machine can be used in the front-wheel, four-wheel
or crab steering mode. The steer select valve (4) controls
the direction of hydraulic fluid flow to the steering cylinder
mounted on each axle. The steer select valve is attached
to a mounting plate inside the frame near the left front
corner of the cab.
Verify the correct operation of the steer select valve
solenoids before considering replacement of the valve.
Refer to Section 9.5, “Electrical System Schematics,” and
Section 9.12, “Display Monitor and Gauges.” The housing
of the steer select valve is not serviceable and must be
replaced if defective.
a. Steer Select Manifold and Valve Removal
1. Park the machine on a firm, level surface, level the
machine, fully retract the boom, lower the boom,
place the transmission control lever in (N) NEUTRAL,
engage the park brake and shut the engine OFF.
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. Properly disconnect the battery.
5. Label, disconnect and cap the hydraulic hoses and
the electrical plugs connected to the steering select
valve.
6. Remove the bolts holding the steer select valve to
the mounting plate on the frame.
7. Remove the steer select manifold with the attached
steer select valve from the machine. Wipe up any
hydraulic fluid spillage in, on, near and around the
machine.
MY0151
2
2
MZ0370
3
MY0350
4