JLG G12-55A Service Manual - Manual (Page 134)

Hydraulic System
8-18 G10-55A, G12-55A
b. Service Brake Valve Installation
1. Install the service brake valve (4) with the four
capscrews, four lockwashers and four nuts (3) onto
the service brake bracket (5).
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.
8.7.4 Service Brake Bleeding
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 located on the front axle (two inner service brake
bleeders and two outer park brake bleeders) and two
service brake bleeders on the rear axle). 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.
2. Remove the plastic cap from one service brake
bleeder (6). 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. Have the assistant depress the brake pedal.
DO NOT open the service 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. Close the service brake
bleeder when air bubbles no longer appear in the oil.
Release the brake pedal. Remove the tubing from
the service brake bleeder.
4. Repeat Steps 2 and 3 for the remaining service
brake bleeders.
5. Check hydraulic oil level and add if necessary.
6. Conduct a pressure and function check of the
service brake. Refer to Section 8.4.1, “ Hydraulic
Pressures.”
MAL0750
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