PAD 6G4954 - Caterpillar

Personal injury or death can result if two persons are not used in the following procedure.
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, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat products.Dispose of all fluids according to local regulations and mandates.
Introduction
This information includes the following procedure:
Brake System Air - PurgeRequired Tools
Table 1
Required Tools    
Quantity     Part Number     Description    
Use As Required         Transparent Tube
6.4 mm (0.25 inch)    Test Preparation
Prepare the machine for testing by completing the procedure that is specified in Testing and Adjusting, "Machine Preparation for Troubleshooting" for the machine that is being serviced.
Illustration 1 g03521717
Steering Frame in the locked position
Move steering frame lock to the LOCKED position.
Stop the engine. Engage the parking brake.Test Procedure
Illustration 2 g03521718
View of the Front Axle Housing (1) Front axle air purge screws.
Illustration 3 g03521719
View of the Rear Axle Housing (2) Rear axle air purge screws.The four air purge screws for the service brakes are located on the top of the corresponding axle housing.Note: Perform this procedure for one service brake at a time.
Check the hydraulic tank oil level. Make sure that you maintain the correct oil level in the hydraulic oil tank throughout the air removal procedure.
Start the engine. Allow the oil pressure to increase to the cut-out pressure.
Fasten one end of a transparent tube that is 6.4 mm (.25 inch) in diameter to an air purge screw. Put the other end of the tube into a suitable container for collecting the hydraulic oil. You may also route the tube back to the hydraulic oil tank. Loosen the air purge screw (1) .
The operator should slowly depress the brake pedal. Hold the brake pedal in this position throughout Step 5.
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 of the other service brakes. Make sure that all air purge screws are tightened.
Fill the hydraulic oil tank, if necessary.Note: If the brake pedal is spongy during the first hours of operation, perform this procedure again.