793B Off-Highway Truck Caterpillar

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Personal injury can result if the machine moves while testing. If the machine begins to move during test, reduce the engine speed immediately and engage the parking brake.

The following tests are used to determine if the service brake, the secondary brake and the parking brake are functional. These tests are not intended to measure the maximum brake holding effort. The brake holding effort that is required to sustain a machine at a specific engine rpm varies depending on the machine. The variations are the differences in the engine setting, in the power train efficiency, and in the brake holding ability, etc.

During the test of the brakes, compare the previous engine rpm and the recent engine rpm. This will determine the system deterioration.

Service Brake Holding Ability Test

1. Fasten the seat belt before you test the brakes.

2. Check the area around the machine. Make sure that the machine is clear of personnel and clear of obstacles.

3. Test the brakes on a dry, level surface.

4. Start the engine. Allow the air system to build up to the operating pressure.

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Illustration 1	g00284661

5. Apply the service brake.

6. Release the parking brake.

7. Move the transmission direction and speed control lever to the FIRST SPEED FORWARD position.

8. Gradually increase the engine speed to 1200 rpm. The machine should not move.

9. Reduce the engine speed to low idle. Move the transmission direction and speed control lever to the NEUTRAL position. Engage the parking brake. Stop the engine.

Secondary Brake Holding Ability Test

1. Fasten the seat belt before you test the brakes.

2. Check the area around the machine. Make sure that the machine is clear of personnel and clear of obstacles.

3. Test the brakes on a dry, level surface.

4. Start the engine and allow the air system to build up to the operating pressure.

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Illustration 2	g00295764

Note: This can be seen on machines that are equipped with the Electronic Monitoring System (EMS).

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Illustration 3	g00284662

Note: This can be seen on machines that are equipped with the Vital Information Management System (VIMS).

5. Completely move down the secondary brake control.

6. Release the parking brake.

7. Move the transmission direction and speed control lever to the FIRST SPEED FORWARD position.

8. Gradually increase the engine speed to 1200 rpm. The machine should not move.

9. Reduce the engine speed to low idle. Move the transmission direction and speed control lever to the NEUTRAL position. Engage the parking brake. Stop the engine.

Parking Brake Holding Ability Test

1. Fasten the seat belt before you test the brakes.

2. Check the area around the machine. Make sure that the machine is clear of personnel and clear of obstacles.

3. Test the brakes on a dry, level surface.

4. Start the engine and allow the air system to build up to the operating pressure.

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Illustration 4	g00295768

Note: This can be seen on machines that are equipped with the Electronic Monitoring System (EMS).

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Illustration 5	g00284659

Note: This can be seen on machines that are equipped with the Vital Information Management System (VIMS).

5. Engage the parking brake.

6. Move the transmission direction and speed control lever to the FIRST SPEED FORWARD position.

7. Gradually increase the engine speed to 1200 rpm. The machine should not move.

8. Reduce the engine speed to low idle. Move the transmission direction and speed control lever to the NEUTRAL position. Leave the parking brake engaged. Stop the engine.