ENGINE AR 2W8219 - Caterpillar

Improper guide pin adjustment or loose adjusting screw may account for the guide pin contacting the brake disc.
Illustration 29 g02722167
Carrier detached from guide pins.If the gap is too large, the carrier assembly can slide off the pin and detach from the caliper.In this case, the carrier assembly has detached from the guide pins (See Illustration 29). The pin should be 2.4 0.8 mm (0.095 0.032 inch) from the brake disc.Hydraulic Malfunctions
Although uncommon, certain hydraulic malfunctions can prevent the carrier assembly from retracting, causing premature wear. If the brake valve sticks open or if the tank pressure is too high, the brake system will not allow the carrier assembly to retract.Corrective Actions
Normal Wear
Under normal conditions, the friction material on each caliper in a wheel group should wear evenly. Caterpillar recommends checking the width of the friction material every 500 hours. The OMM details instructions on brake wear identification and replacement practices. Maximum brake life is determined by application and operator efficiency. Adverse environmental conditions, such as saltwater, significant amounts of debris, and overuse will cause accelerated wear. The thickness of the friction material should never be less than 3.175 mm (0.125 inch).Troubleshooting Root Cause of Brake Failure
When the operator complains of poor brake performance or abnormal sounds, inspect the machine. If the visual inspection indicates there is an issue with the brake system, a root cause must be identified. Check the following failure modes to determine the root cause of the failure.Note: Perform the following steps in the order given.
Calipers not retracting due to excessive back pressure: If the pressure at any wheel group does not fall below 130 kPa (18 psi) when the service brake is released, the friction material may continue to be pressed against the brake disc. This failure mode could be due to poor manufacturing or because the brake control valve sticks open. If the tank pressure is too high, the service brakes may drag.
Verify that the brake pressure at each wheel group is greater than 14,000 kPa (2030 psi) when the brakes are pressed and below 130 kPa (18 psi) when the brakes are released.
Verify that the tank pressure is below 20 kPa (3 psi)
Verify that the breather is functioning properly.
Operator Overuse Due to Transmission Retarder Inefficiency: If the transmission retarder is inoperable, the operator will use the service brakes as the primary retarder. Verify that the transmission retarder and retarder lever are functioning properly before checking other failure modes.
Operator Overuse Due to Misuse of Transmission Retarder: The most common failure mode on dry brakes is one where the operator uses the service brakes as the primary retarder on the machine. In this case, the friction material will crack and crumble off the carrier assembly. The brake disc may warp and show signs of overheating (see Section 2). This results in tapered linings because of the temperature difference across the lining. Verify that the operator is properly trained before operating the machine. The OMM details proper use of the transmission retarder.
Caliper Not Retracting