Personal injury or death can result if two persons are not used in the following procedure. |
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. |
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, "AVSpare Tools and Shop Products Guide" for tools and supplies suitable to collect and contain fluids on AVSpare products. Dispose of all fluids according to local regulations and mandates. |
Purge the Air from the Service Brakes and Retarder
- Check the hydraulic tank oil level. Make sure that you maintain the correct oil level in the hydraulic tank throughout the air removal procedure.
Note: Purge only one wheel at a time.
- Start the engine. Allow the braking system oil pressure to increase to the cut-out pressure. Keep the engine running at low idle throughout the air removal procedure.
- Engage the parking brake. Install the steering frame lock.
- Connect one end of a transparent tube that is 6.4 mm (0.25 inch) in diameter to purge screw (4) for the service brake and retarder section of the left front wheel brake. Put the other end of the tube into a suitable container for collecting the hydraulic oil.
Illustration 1 | g00996867 |
Location of the purge screw manifold for the front wheel brakes |
Illustration 2 | g00996868 |
(1) Purge screw for the right front parking brake (2) Purge screw for the left front parking brake (3) Purge screw for the right front service brake and retarder section of the wheel brake (4) Purge screw for the left front service brake and retarder section of the wheel brake |
- Have an assistant depress and hold down the service brake pedal. Hold the brake pedal in this position throughout Step 6.
- Open purge screw (4). 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 purge screw. Release the service brake pedal.
- Move the retarder control lever to the full ON position. Leave the retarder control lever in this position throughout Step 8.
- Open purge screw (4). Turn the purge 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 purge screw. Move the retarder control lever to the OFF position.
- Perform this procedure for the right front wheel brake.
- Connect one end of a transparent tube that is 6.4 mm (0.25 inch) in diameter to purge screw (5) for the service brake and retarder section of the left rear wheel brake. Put the other end of the tube into a suitable container for collecting the hydraulic oil.
Illustration 3 | g00997865 |
Typical rear view of a rear wheel brake assembly (5) Purge screw for the service brake and retarder (6) Purge screw for the parking brake |
- Have an assistant depress and hold down the service brake pedal. Hold the brake pedal in this position throughout Step 12.
- Open purge screw (5). Turn the purge 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 purge screw. Release the service brake pedal.
- Move the retarder control lever to the full ON position. Leave the retarder control lever in this position throughout Step 14.
- Open purge screw (5). Turn the purge 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 purge screw. Move the retarder control lever to the OFF position.
- Perform this procedure for the right rear wheel brake.
- After the air has been removed, be sure all purge screws are closed. 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 16 until no air is present in the service brake system.
Purge the Air from the Parking Brake
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. |
- Check the hydraulic tank oil level. Make sure that you maintain the correct oil level in the hydraulic tank throughout the air removal procedure.
Note: Purge only one wheel at a time.
- Start the engine. Allow the braking system oil pressure to increase to the cut-out pressure. Keep the engine running at low idle throughout the air removal procedure.
- Engage the parking brake. Install the steering frame lock.
- Have an assistant move the parking brake switch to the OFF position to disengage the parking brake.
- Connect one end of a transparent tube that is 6.4 mm (0.25 inch) in diameter to parking brake purge screw (2) for the left front wheel brake. Put the other end of the tube into a suitable container for collecting the hydraulic oil.
Illustration 4 | g00996868 |
(1) Purge screw for the right front parking brake (2) Purge screw for the left front parking brake (3) Purge screw for the right front service brake and retarder section of the wheel brake (4) Purge screw for the left front service brake and retarder section of the wheel brake |
- Open the purge screw. Turn the purge 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 purge screw.
- Perform this procedure for the right front wheel brake.
- Connect one end of a transparent tube that is 6.4 mm (0.25 inch) in diameter to purge screw (6) for the parking brake section of the left rear wheel brake. Put the other end of the tube into a suitable container for collecting the hydraulic oil.
Illustration 5 | g00997865 |
Typical rear view of a rear wheel brake assembly (5) Purge screw for the service brake and retarder (6) Purge screw for the parking brake |
- Open the purge screw. Turn the purge 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 purge screw.
- Perform this procedure for the right rear wheel brake.
- After the air has been removed, be sure all 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 11 until no air is present in the parking brake system.