JLG G6-42A Service Manual - Manual (Page 156)

Hydraulic System
8-22 G6-42A, G9-43A, G10-43A
9. Install the main control valve protective cover.
10. Close and secure the engine cover.
11. Remove the Do Not Operate Tags from both the
ignition key switch and the steering wheel.
g. Main Control Valve Test
Conduct a pressure check of the hydraulic system in its
entirety. Adjust pressure(s) as required. Refer to Section
8.3.1, “Pressure Checks and Adjustments.”
8.7.2 Service Brake Valve
a. Service Brake 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 all hose attached to the
service brake valve (1).
6. Remove the service brake pedal. Refer to Section
4.3.2, “Service Brake Pedal.”
7. Remove the four capscrews, four nuts and four
lockwashers mounting the service brake valve to the
service brake bracket.
Note: DO NOT disassemble the service brake valve.
The service brake valve is not serviceable and must be
replaced in its entirety, if defective.
b. Service Brake Valve Installation
1. Install the service brake valve with the four
capscrews, four lockwashers and four nuts onto the
service brake bracket.
2. Install the service brake pedal. Refer to Section
4.3.2, “Service Brake Pedal.”
Note: ALWAYS replace seals, o-rings, gaskets, etc.,
with new parts to help ensure proper sealing and
operation. Lubricate seals and o-rings with clean
hydraulic oil.
3. Use new oiled o-rings as required. Uncap and
connect the previously labeled hoses to the service
brake valve.
4. Check the routing of all hoses, and tubing for sharp
bends or interference with any rotating members,
and install tie wraps and/or protective conduit as
required. Tighten all tube and hose clamps.
5. Properly connect the battery.
6. 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.
7. Inspect the service brake valve and connections for
leaks, and check the level of the hydraulic fluid in the
reservoir. Shut the engine OFF.
Note: Check for leaks, and repair as required before
continuing. Add hydraulic fluid to the reservoir as
needed.
8. Wipe up any hydraulic fluid spillage in, on, near and
around the machine, work area and tools.
9. Close and secure the engine cover.
10. Remove the Do Not Operate Tags from both the
ignition key switch and the steering wheel.
8.7.3 Brake Test
Carefully bleed the brake lines as soon as the brake valve
is installed in the machine. Air in the system will not allow
the brakes to apply properly. There are four brake
bleeder locations on the axles. Work with an assistant to
perform this procedure.
1. Place the travel select lever in (N) NEUTRAL,
engage the park brake, and start the engine.
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