777G Off-Highway Truck Hydraulic and Braking System Caterpillar

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Personal injury or death can result from machine movement. Place blocks in front of and behind the wheels to make sure the machine does not move while the parking brakes are disengaged.

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Personal injury or death can result from sudden machine movement. Sudden movement of the machine or release of air pressure or oil pressure can cause injury to persons on or near the machine. To help prevent possible injury before testing and adjusting any air system or hydraulic system, perform the procedure in the Testing and Adjusting, "General Information" section.

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Illustration 1	g02322613
(1) Pressure tap at the rear of the machine

1. While the engine is off, and the parking brake is engaged, install the 198-4240 Digital Pressure Indicator to pressure tap (1) at the rear of the machine.

2. Start the engine. Operate the engine and warm the brake oil until the brake oil reaches a temperature of 82° ± 10°C (180° ± 20°F).

3. With the engine in low idle, fully apply the service brakes and move the gear selector to the NEUTRAL position.

   • Secondary brake pressure at pressure tap (1) should rise to 5033 ± 690 kPa (730 ± 100 psi) .

4. With the gear selector in the NEUTRAL position, fully apply the secondary brake pedal.

   • Secondary brake pressure at pressure tap (1) should drop to less than 140 kPa (20.0 psi).

5. Fully release the secondary brake pedal.

6. While the service brake pedal is fully applied, and while the gear selector is in the NEUTRAL position, shut off the engine.

   Note: Use the ground level emergency shutdown switch in order to shut off the engine.

   • Secondary brake pressure at pressure tap (1) should remain above 3800 kPa (550.0 psi) for one minute.

7. Fully apply the secondary brake pedal.

   • Secondary brake pressure at pressure tap (1) should be less than 140 kPa (20.0 psi).

8. Move the gear selector to the PARK position and release the secondary brake pedal and the service brake pedal.

9. Stop the engine.

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Personal injury or death can result from sudden machine movement. Sudden movement of the machine or the release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury before testing and adjusting the hydraulic system, perform the procedure in the Testing and Adjusting, "General Information" section.

Note: Make sure that you remove all air from the hydraulic brake system. See the Testing and Adjusting, "Brake System Air - Purge" for the procedure.