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A change in the braking characteristics or a low pressure warning may be an indication of a failure in one of the brake circuits. Personal injury or death may occur if the machine is operated before repairs have been made or before all circuits have been checked. Always check the brakes after brake repairs have been made and before the machine is put back into use. |
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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 Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Caterpillar products. Dispose of all fluids according to local regulations and mandates. |
ReferenceFor more information on preparing the machine for troubleshooting, refer to the Service Manual module Testing and Adjusting, "Machine Preparation for Troubleshooting".
Brake service life can vary greatly because of the different applications and operator technique.
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.
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| Illustration 1 | g00881296 |
Service Brake (1) Friction disc (2) Plate | |
It is very important to change friction disc (1) 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 (2). This problem is known as spalling.
Spalling will destroy the very smooth surface finish of plates (2). 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 service brake disc (1) 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.
The thickness of a new friction disc (1) is 9.10 ± .13 mm (.358 ± .005 inch).
The recommended minimum thickness of a worn friction disc is 8.05 mm (.317 inch).
Replace friction disc (1) when the minimum thickness is reached.
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. If the depth of the grooves on the service brake discs are too shallow, oil flow to the service brakes will be inadequate. The oil flow cools the brakes.
- Check the groove depth on both sides of the service brake disc. Check all service brake discs in each service brake.
- The depth of the oil grooves must be greater than 0.53 mm (.021 inch).
| Disc Thickness Wear Chart | ||
| Estimated Percentage of Remaining Brake Disc Life | Width of Disc | Oil Groove Depth (1) |
| 100 | 9.1 mm (.358 inch) |
1.05 mm (.041 inch) |
| 80 | 8.89 mm (.350 inch) |
0.95 mm (.037 inch) |
| 60 | 8.68 mm (.342 inch) |
0.84 mm (.033 inch) |
| 40 | 8.48 mm (.334 inch) |
0.74 mm (.029 inch) |
| 20 | 8.27 mm (.326 inch) |
0.63 mm (.025 inch) |
| 0 | 8.05 mm (.317 inch) |
0.53 mm (.021 inch) |
| ( 1 ) | Groove depth is the most critical measurement. |
Note: In order to calculate the maximum wear of the oil groove depth, 50% of the new groove depth is used.
ReferenceFor 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.