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Personal injury or death can result if two persons are not used in the following procedure. |
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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. |
Machine Preparation
Prepare the machine for testing by completing the procedure that is specified in the Service Manual module Testing and Adjusting, "Machine Preparation for Troubleshooting" for the machine that is being serviced.
Test Procedure
Brake service life can vary greatly because of the different applications. The following conditions can lead to premature brake failure:
- Check for oil leaks at the yoke and the drive axles. A leak can also allow contamination from water and debris to occur. Water and debris can enter the axle through the lip seal at the drive yoke. The water and debris can mix with the oil. This water and debris can lead to premature brake failure.
- The axle housing breather may be plugged or damaged. Check the axle housing breather for proper operation.
- Excessive heat can be generated if the service brakes are used as a retarder. Excessive heat can be generated if the service brakes are used as a device to maintain a slower ground speed. This type of operation should be avoided by using a lower transmission gear speed.
Check the grooves on both sides of each disc in both the front and rear service brakes. The wear of the service brake disc may vary from one end of the machine to the other end, and from one side of the machine to the other side. The estimated wear for a given groove depth is shown in table 1.
Also, it is very important to change the friction discs as soon as possible once the groove depth has reached the maximum wear limit. As the depth of the grooves is reduced, the flow of the cooling oil is reduced. This causes heat to build up. The heat causes the rapid wear of the disc material. Eventually, the friction material will wear off the disc. This will cause metal to metal contact between the disc and plates. This problem is known as spalling.
The buildup of the friction material in the oil could cause damage to the very smooth surface finish of the plate. Spalling will destroy the very smooth surface finish of the plate. This will make replacement of these brake components necessary.
If the failure has progressed to metal to metal contact, the complete axle must be thoroughly cleaned. This process of cleaning the axle must be done correctly, or the debris will continue to contaminate the oil. This will cause the material on the service brake disc to wear rapidly. This condition will cause premature failure of the service brakes.
If excessive brake wear or premature brake wear is suspected, perform a scheduled oil sampling. This report could help establish a possible cause for failure of the service brakes.
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| Illustration 1 | g00478200 |
Components of the Service Brakes (A) Thickness of a disc. (1) Piston. (2) Disc. (3) Plate. | |
- The thickness (A) of a new disc (2) is 7.10 ± 0.13 mm (0.280 ± 0.005 inch). The minimum thickness (A) of a worn disc (2) should not exceed 5.70 mm (0.224 inch). Service the brake before disc (2) reaches the minimum thickness (A).
Note: Check each service brake disc in each service brake.
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| Illustration 2 | g00478267 |
Measuring the Depth of the Oil Grooves on the Service Brake Disc | |
Note: Groove depth is the most critical dimension. The oil flow will be inadequate to the service brakes. If the depth of the grooves on the service brake discs are too shallow, oil flow to the service brakes will be inadequate.
- Check the groove depth on both sides of the service brake disc. Use a wire gauge for this procedure. Check all service brake discs in each service brake.
- The depth of the oil grooves must be greater than 0.46 mm (0.018 inch).
| Disc Thickness Wear Chart | ||
| Estimated Percentage of Remaining Brake Disc Life | Remaining Thickness of Disc | Oil Groove Depth (1) |
| 100 | 7.10 mm (.280 inch) |
1.05 mm (.041 inch) |
| 80 | 6.86 mm (.270 inch) |
0.93 mm (.037 inch) |
| 60 | 6.62 mm (.261 inch) |
0.81 mm (.032 inch) |
| 40 | 6.40 mm (.252 inch) |
0.70 mm (.027 inch) |
| 20 | 6.16 mm (.243 inch) |
0.58 mm (.023 inch) |
| 0 | 5.92 mm (.233 inch) |
0.46 mm (.018 inch) |
| ( 1 ) | Groove depth is the most critical measurement. |
Reference: For more information on checking the service brakes, refer to the Service Manual module Disassembly and Assembly, "Final Drive and Brake Assemblies" for the machine that is being serviced.