JLG G6-23A Service Manual - Manual (Page 84)

Hydraulic System
8.14 G5-19A, G6-23A
2. Use new oiled o-rings as required. Uncap, reattach
and secure the three hoses.
3. Check the routing of all hoses for sharp bends or
interference with any rotating members, and install
tie wraps and/or protective conduit as required.
4. Start the engine and run at approximately one-third
to one-half throttle for about one minute, without
moving the machine or operating any hydraulic
functions.
5. Inspect the park brake valve and connections for
leaks, and check the level of the hydraulic fluid in the
reservoir. Shut the engine OFF.
6. Replace the brake valve cover.
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.
Note: The park brake valve circuit will need to be bled
after installation. Refer to Section 8.10.4, “Brake Test.”
8.10.4 Brake Test
Carefully bleed the brake lines as soon as the brake valve
is installed on the machine. Air in the system will not allow
the brakes to apply properly. There are four brake
bleeder locations (3) on the front axle. The outside
bleeders are used for the park brake circuit. The inside
bleeders are used for the service brake circuit. Work with
an assistant to perform this procedure.
1. Place the transmission control lever in
(N) NEUTRAL, engage the park brake, and start the
engine.
2. Remove the plastic cap from the brake bleeder.
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 12 mm
wrench. Have an 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
bleeder.
5. If bleeding the service brake circuit, 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.
Refer to Section 2.4, “Fluids, Lubricants and
Capacities.”
7. Conduct a pressure and function check of the brake.
8.10.5 Steering Orbitrol Valve
Refer to Section 4.3.2, “Steering Column/Valve
Replacement,” for details.
8.10.6 Steer Select Valve
The steer select valve is attached to a manifold mounted
on a mounting plate inside the frame near the front drive
motor.
Verify the correct operation of the steer select valve
solenoids before considering replacement of the valve.
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, 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 an Do Not Operate Tag on both the ignition
key switch and the steering wheel, stating that the
machine should not be operated.
3. Open the engine cover. Allow the system fluids to
cool.
4. Label or otherwise mark the hydraulic hoses in
relation to the steer select manifold. Disconnect and
cap all hoses, fittings, solenoid wire terminal leads,
etc.
5. Remove the capscrews that attach the manifold to
the frame.
MAH1060
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