| NOTICE |
|---|
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting and repair of the machine. 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 in Caterpillar machines. Dispose of all fluids according to local regulations and mandates. |
| Tools Needed | |
| 8T-5320 Hydraulic Testing Group | 1 |
| 4C-4890 Hydraulic Test Group | 1 |
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| Illustration 1 | g00346868 |
Location for pressure tap (M) | |
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| Illustration 2 | g00343774 |
Location for pressure tap (N) | |
This test will show if the parking brake release pump section is working properly. This test will also show if the relief valve for the parking brake release system is set correctly.
- Remove the plug at location (M) or (N) . Install a nipple at the location of the removed plug.
- With a coupler and a hose, install a 8T-0856 Pressure Gauge (0 to 6000 kPa (0 to 870 psi)) to nipple (M) or (N) .
- While the parking brakes are activated, start the engine. Operate the engine at high idle rpm. The transmission should be in NEUTRAL. The pressure on the gauge must be at the relief valve setting.
Show/hide table
Table 2 Model Serial Range Relief Valve Setting 784B
785B
789B5RK1-13
6HK1-331
7EK1-273
4100 ± 200 kPa (595 ± 29 psi)784B
785B
789B5RK14-UP
6HK332-UP
7EK274-UP
4690 ± 200 kPa (680 ± 29 psi)
- If the setting of relief valve (3) for the parking brake release system is too low, perform the following procedure:
- Remove cap (1) . Loosen nut (2) .
- Turn the threaded rod clockwise in order to increase pressure. One turn increases the setting approximately 690 kPa (100 psi) .
- Remove cap (1) . Loosen nut (2) .
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| Illustration 3 | g00281783 |
Parking and secondary brake valve (1) Cap (2) Nut (3) Relief valve for parking brake release system | |
- If the setting of relief valve (3) for the parking brake release system is too high, perform the following procedure:
- Remove cap (1) . Loosen nut (2) .
- Turn the threaded rod counterclockwise in order to decrease pressure. One turn decreases the setting approximately 690 kPa (100 psi) .
- Remove cap (1) . Loosen nut (2) .
- Tighten nut (2) . Replace cap (1) .
- When you complete the test, stop the engine. Remove the test equipment.