JLG 723A Service Manual - Manual (Page 99)

8-17 L2906H, 2906H, 3507H, 619A, 723A, 29.6LP, 29.6, 35.7
Hydraulic System
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.
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 oil in the
reservoir. Shut the engine OFF.
6. Replace the brake valve cover.
7. Wipe up any hydraulic oil spillage in, on, near and
around the machine, work area and tools.
8. Close and secure the engine cover.
9. Remove the Do Not Operate Tags from both the
ignition key switch and the steering wheel.
Note: The park brake valve circuit will need to be bled
after installation. Refer to Section 8.11.4, “Brake Test.”
8.11.4 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 (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.
c. Park Brake Valve Installation
1. Install the park brake valve with the two lockwashers
and two capscrews to the cover.
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.
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 oil in the
reservoir. Shut the engine OFF.
6. Install the park brake/cover with the four capscrews.
7. Wipe up any hydraulic oil spillage in, on, near and
around the machine, work area and tools.
MAH1060
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