The parking brake is intended to hold the machine stationary after the machine has come to a complete stop. The parking brakes are mounted in the brake packs on each front wheel. The next portion of the story describes the parking brake operation The parking brake is applied by spring pressure. The parking brake is released by oil pressure.
Location of Components and Functions
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| Illustration 1 | g03344520 |
| (1) Parking brake switch | |
The monitoring system is located in the operator console.
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| Illustration 2 | g03344358 |
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The location of the park brake indicator is typical. (2) Parking brake indicator | |
The monitoring system is located in the operator console.
Reference: Refer to the Monitoring System Systems Operations for your machine for additional information.
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| Illustration 3 | g03428088 |
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| Illustration 4 | g03893121 |
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| Illustration 5 | g03720963 |
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Close up view of the parking brake control valve. (3) Parking brake solenoid (4) Pressure sensor | |
The parking brake switch (1) allows the operator to turn the parking brake on and off. The parking brake indicator (2) shows that the parking brake is engaged or disengaged. The parking brakes are the same brake pack that is used for the service brakes. The parking brake compresses the brake pack to prevent the machine from moving. The pressure sensor (4) informs the ECM that the parking brake is either on or OFF. The parking brake solenoid (3) controls the flow of oil to the parking brake and from the parking brake. The parking brake is OFF when the solenoid is energized. The parking brake is on when the solenoid is de-energized.
The Parking Brake Solenoid De-energized
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| Illustration 6 | g03419083 |
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(5) Piston
(6) Springs (7) Cavity (8) Anchor (9) Plate (10) Brake disc | |
When the engine is being started or when the parking brake switch (1) is in the ON position, the parking brake solenoid (3) is de-energized. When the parking brake solenoid is de-energized, oil is drained from cavity (7). Pressure from springs (6) moves piston (5). The piston compresses the plates (9) and the brake discs (10). The plates (9) are splined to anchor (8). The anchor is splined to the wheel spindles. The brake disks (10) are splined to the wheels. Wheel rotation is prevented when plates (9) and brake discs (10) are compressed. The pressure sensor (4) sends a signal to the ECM. The ECM turns on the parking brake indicator in order to inform the operator that the parking brake is engaged.
The Parking Brake Solenoid Energized
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| Illustration 7 | g03419127 |
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(5) Piston
(6) Springs (7) Cavity (8) Anchor (9) Plate (10) Brake disc | |
When the parking brake switch (1) is in the OFF position, the parking brake solenoid (3) is energized. When the parking brake solenoid is energized, the solenoid shifts because the valve pressure is greater than the spring pressure. Oil is sent into cavity (7) from the pump. Oil pressure moves piston (5). The piston compresses the springs (6). The plates (9) are splined to anchor (8). The anchor is splined to the wheel spindles. The brake disks (10) are splined to the wheel. The wheel and the brake discs (10) are free to turn when springs (6) are compressed. The pressure switch sends a signal to the ECM. The ECM turns off the parking brake indicator in order to inform the operator that the parking brake is disengaged.