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Personal injury or death can result if two persons are not used in the following procedure. |
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Personal injury or death can result from air in the oil for the brake hydraulic system. Air in the system can prevent complete brake application and it is possible that the wheels on the machine can not be stopped. Air must not be in the oil for the brake hydraulic system to function properly. |
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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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| NOTICE |
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Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids. Refer to Special Publication, NENG2500, "Caterpillar Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on Caterpillar products. Dispose of all fluids according to local regulations and mandates. |
Purge the Air from the Service Brakes
- Check the hydraulic tank oil level. Make sure that you maintain the correct oil level in the hydraulic tank throughout the air removal procedure.
- Engage the parking brake and stop the engine. Install the steering frame lock. Place blocks in front of the wheels and behind the wheels.
- Start the engine. Allow the braking system oil pressure to increase to the cut-out pressure.
- Disengage the parking brake. Keep the engine running and maintain the brake accumulator pressure within working limits throughout the air removal procedure.
- Have an assistant slowly depress the brake pedal, holding it down for at least 20 seconds. Repeat this procedure three times, with a 30 second wait between each depressing of the brake pedal.
- Connect one end of a transparent tube that is 6.4 mm (0.25 inch) in diameter to the service brake air purge screw, put the other end of the tube into a suitable container for collecting the hydraulic oil.
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| Illustration 1 | g01254085 |
(1) Air purge screw for front brakes | |
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| Illustration 2 | g01268944 |
(2) Air purge screw for rear brakes | |
- Have the assistant slowly depress the brake pedal. Hold the brake pedal in this position throughout Step 8.
- Open the air purge screw. Turn the valve one-half turn to permit oil flow through the tube. As the hydraulic oil flows through the tube, look for air bubbles in the oil. Allow the oil to flow into the container until no air bubbles are visible. Then, tighten the air purge screw.
- Release the brake pedal.
- Perform this procedure for each wheel brake, but do only one wheel brake at a time. After the air has been removed, be sure all air purge screws are closed.
- Engage the parking brake and stop the engine. Fill the hydraulic tank, if necessary.
- If the brakes feel soft during application in the first few hours of operation, repeat Steps 1 through 11 until no air is present in the service brake system.
Purge the Air from the Parking Brake
- To allow access to the front wheel brake assemblies, raise the lift arms and install the lift arm support pins.
ReferenceRefer to Operation and Maintenance Manual, "Lift Arm Support Pins".
- Check the hydraulic tank oil level. Make sure that you maintain the correct oil level in the hydraulic tank throughout the air removal procedure.
- Engage the parking brake and stop the engine. Install the steering frame lock. Put blocks in front of the wheels and behind the wheels.
- Remove cover (1) from each front wheel brake assembly.
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| Illustration 3 | g01254088 |
(1) Cover | |
- Start the engine. Disengage the parking brake. Keep the engine running and maintain the brake accumulator pressure within working limits throughout the air removal procedure.
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| Illustration 4 | g01254089 |
(2) Air purge screw for front parking brake | |
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| Illustration 5 | g01268946 |
(3) Air purge screw for rear parking brake | |
- Connect one end of a transparent tube that is 6.4 mm (0.25 inch) in diameter to the parking brake air purge screw. Put the other end of the tube into a suitable container for collecting the hydraulic oil.
- Open the air purge screw. Turn the screw one-half turn to permit oil flow through the tube. As the hydraulic oil flows through the tube, look for air bubbles in the oil. Allow the oil to flow into the container until no air bubbles are visible. Then tighten the air purge screw.
- Perform this procedure for each wheel brake, but do only one wheel brake at a time. After the air has been removed, be sure all air purge screws are closed.
- Engage the parking brake and stop the engine. Fill the hydraulic tank, if necessary.
- If the parking brakes are not correctly disengaging, repeat Steps 1 through 9 until no air is present in the parking brake system.