Escaping fluid under pressure, even a pinhole size leak, can penetrate body tissue, causing serious injury, and possible death. If fluid is injected into your skin, it must be treated immediately by a doctor familiar with this type of injury. Always use a board or cardboard when checking for a leak. |
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. Complete the following procedures that are specified in the Service Manual for the machine that is being serviced.
- Testing and Adjusting, "Machine Preparation for Troubleshooting"
- Testing and Adjusting, "System Pressure - Release"
Testing and Adjusting Procedure
This procedure should be used to check the service brake control valve for excessive internal leakage. In order to check the service brake control valve for excessive internal leakage, the drain lines for the front and rear service brakes must be removed from the service brake control valve.
Note: Make sure that the precharge pressure of the brake accumulators are within specifications before running this procedure.
Reference: For more information on accumulators, refer to the Service Manual module Testing and Adjusting, "Brake Accumulator - Test and Charge" for the machine that is being serviced.
Reference: For more information on the specifications of the brake accumulators, refer to the Service Manual module Specifications, "Brake Accumulator" for the machine that is being serviced.
Illustration 1 | g00467194 |
Location of the Service Brake Control Valve (1) Drain line to the rear service brakes. (2) Drain line to the front service brakes. (3) Service brake control valve. |
Service brake control valve (3) is located under the cab just behind the steering shaft.
- Remove drain line (1) and (2) at service brake control valve (3) .
- Start the engine. Bring the hydraulic oil to operating temperature.
- Measure the flow of oil from the top port with the charging system at cut-out pressure. The flow must be less than 0.2 L/min (0.05 US gpm).
- Measure the flow of oil from the bottom port with the charging system at cut-out pressure. The flow must be less than 0.1 L/min (0.03 US gpm).
- If the flow rates are not correct, then the service brake control valve may have excessive internal leakage back to the hydraulic oil tank. Repair or replacement of the service brake control valve may be required.