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Hot oil and hot components can cause personal injury. Do not allow hot oil or hot components to contact skin. |
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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. |
The service brakes should only require purging after disassembly of the brake system components.
If service has been carried out on the service brakes for the front axle, only the front brake lines should need purging.
If service has been carried out on the service brakes on the trailer, only the lines for these brakes should need purging.
Note: If the lines for the brake accumulator have been serviced, always purge the lines for the brake accumulator before attempting to purge the lines for the brakes. The purge screws are located on the check and pressure reducing valve.
In order to purge the brakes, start with the bleed fitting at the greatest distance from the service brake control valve and work back to the line for the brake closest to the brake control valve.
- Attach lengths of clear tubing to the upper bleed fitting for the appropriate brake. Fix the free ends into a suitable container.
Note: There are two bleed fittings on each brake caliper. One bleed fitting is located above the axle and the other bleed fitting is located below the axle.
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| Illustration 1 | g00754723 |
Bleed fittings for the service brakes with the twin calipers. | |
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| Illustration 2 | g00754725 |
Bleed fittings for the service brakes with the single calipers. | |
- Move the transmission control to the NEUTRAL position and move the parking brake control to the ENGAGED position. Start the engine and operate the engine at low idle.
- Open the bleed fittings. Have an assistant slowly and carefully press the service brake pedal until air and/or oil is discharged from the tubes.
Slowly press the brake pedal in order to just connect the lines for the accumulator to the lines for the brakes. Oil will slowly flow into the lines for the brakes and the oil will force any air out of the lines.
- When the oil flows free of air, close the bleed fittings and release the brake pedal.
- Repeat the procedure for each brake caliper in the system.
- Check the hydraulic oil level. Refer to Operation and Maintenance Manual, SEBU7347, "Hoist, Steering, and Brake System Oil Level - Check".
- Wipe up any spilled oil. Dispose of used oil and oil soaked rags according to local environmental regulations.
Normally, if the lines between the service brake control valve and the brakes have been disturbed, one brake application will be enough to purge the air from the system.
If the lines between the accumulator and the service brake control valve have been disturbed, more than one brake application may be required to fully purge the air from the system.