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Personal injury or death can result if two persons are not used in the following procedure. |
| 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, "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. |
| Disc Thickness Wear Chart | ||
| Estimated Percentage of Remaining Brake Disc Life | Remaining Thickness of Disc | Oil Groove Depth(1) |
| 100 | |
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| 80 | |
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| 60 | |
|
| 40 | |
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| 20 | |
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| 0 | |
|
| (1) | Groove depth is the most critical measurement. |
The following information outlines the procedure needed to check the service brake discs.
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| Illustration 1 | g03409100 |
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Components of the Service Brakes (A) Thickness of a new disc (1) Piston (2) Disc (3) Plate | |
The thickness of a new disc (2) is
The minimum thickness of a worn disc (1) is
Service the brake before disc (2) reaches the minimum thickness.
Note: Check each service brake disc in each service brake.
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.
The buildup of the friction material in the oil could damage the smooth surface finish of the plate. Spalling will destroy the smooth surface finish of the plate. This action will make replacement of these brake components necessary.
If the failure has progressed to metal-to-metal contact, thoroughly clean the complete axle. This process of cleaning the axle must be done correctly, or the debris will continue to contaminate the oil. This contamination 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.
The condition of the friction disc is important. 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 action will cause metal to metal contact between the disc and plates. This problem is known as spalling.
- Move the machine to a location that is smooth, level, and hard. The location should also be dry and free of debris. Stop the engine.
- Permit only one operator on the machine. All other personnel should be kept away from the machine.
- Engage the parking brake. Lower the bucket or attachment to the ground. Put blocks in front of the wheels, and put blocks behind the wheels.
- Install the steering frame lock link.
- To relieve any brake oil pressure, push the brake pedal a minimum of a 100 times.
- Remove the service brake from the machine and disassemble. Refer to the Disassembly and Assembly, "Final Drive and Brake Assemblies" for more information.
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. The wear of the service brake disc may vary from one side of the machine to the other side. The estimated wear for a given groove depth is shown in table 1
The thickness of a new disc is
The minimum thickness of a worn disc is
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| Illustration 2 | g03404564 |
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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. When the depth of the grooves on the service brake discs is 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
0.32 mm (0.013 inch) Note: Service the brake before disc reaches the minimum thickness.