JLG G12-55A Service Manual - Manual (Page 135)

8-19 G10-55A, G12-55A
Hydraulic System
8.7.5 Service Brake Test
This procedure is used in order to determine if the service
brake is functional. This procedure is not intended to
measure the maximum brake performance. the brake
holding torque that is required to sustain an engine torque
at a specific engine rpm varies depending on the machine
configuration. The variations are the differences in the
engine settings, power train efficiency and in the brake
holding ability, etc.
Conduct the following service brake test on a dry level
surface, clear of any personnel and/or obstacles.
1. Place the travel select lever in (N) NEUTRAL,
engage the park brake, and start the engine.
2. Raise the boom to a travel position.
3. Depress the service brake, disengage the parking
brake and place the travel select lever in third gear
forward.
4. Smoothly and controllably depress the throttle pedal.
Note: Do Not hold the accelerator pedal in the fully
depressed position for more than ten seconds. Damage
to the power train could occur.
5. Smoothly and controllably fully release the throttle
pedal.
6. The machine should remain stationary during the
test.
7. If the machine does not remain stationary during this
test, contact the local distributor for proper service.
8. Engage the park brake, place the travel select lever
in (N) NEUTRAL, lower the boom and shut engine
OFF.
8.7.6 Park Brake Test
This procedure is used in order to determine if the parking
brake is functional. This procedure is not intended to
measure the maximum brake performance. the brake
holding torque that is required to sustain an engine torque
at a specific engine rpm varies depending on the machine
configuration. The variations are the differences in the
engine settings, power train efficiency and in the brake
holding ability, etc.
Conduct the following parking brake test on a dry level
surface, clear of any personnel and/or obstacles.
1. Place the travel select lever in (N) NEUTRAL,
engage the park brake, and start the engine.
2. Raise the boom to a travel position.
3. Depress the service brake, disengage and place the
travel select lever in first gear forward.
4. Smoothly and controllably release the service brake.
5. Smoothly and controllably depress the throttle pedal.
Note: Do Not hold the accelerator pedal in the fully
depressed position for more than ten seconds. Damage
to the power train could occur.
6. Smoothly and controllably fully release the throttle
pedal.
7. The machine should remain stationary during the
test.
8. If the machine does not remain stationary during this
test, contact the local distributor for proper service.
9. Engage the park brake, place the travel select lever
in (N) NEUTRAL, lower the boom and shut engine
OFF.
8.7.7 Steering Orbitrol Valve
The steering orbitrol valve (7) 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.”
MY4280 7