Park Brake Solenoid Valve Troubleshooting Procedure Caterpillar

Problem:

There have been reports of the Park Brake either failing to engage, or failing to disengage.

Solution:

When troubleshooting the park brake, it may be necessary to check the solenoid valve for correct operation. The following procedure will determine the correct operation and show the appropriate action to be taken. Refer to Table 2 for the appropriate part numbers and specified pressure ranges for each machine.

NOTE: The following procedure must be used in conjunction with the relevant Service Manual; System Operation Testing & Adjusting-Brake System, for the machines listed above.

Park Brake Fails to Disengage

1) With the park brake control in the cab in the "DISENGAGED" position, measure the pump input pressure and the park brake output pressure of the park brake control valve at the ASBS valve.

If the pump input pressure and the park brake output pressure are not within the specified ranges shown in Table 2, check for correct operation of the coil. The correct part number of the coil is shown in Table 1.

Using a digital voltmeter, measure either the current, or the resistance, of the coil. If the current or the resistance are not within the specified ranges shown in Table 1, replace the coil.

2) If the coil is operating within the specified ranges shown in Table 1, perform the following steps:

a) Shut down the machine, and turn off the engine.

b) Purge the pressure in the brake system.

c) Remove and thoroughly clean the cartridge valve.

d) Install the cartridge valve and retest.

3) If the park brake is still not operating correctly, replace the cartridge valve by performing the following steps:

a) If the park brake is still not operating correctly, replace the cartridge valve by performing the following steps:

b) Purge the pressure in the brake system.

c) Remove and the cartridge valve.

d) Install the new cartridge valve and retest.

4) When replacing the cartridge valve, take a sample of the oil from the pump, and a sample of the oil returning from the park brake. Notify Service Engineering and return the cartridge valve, both oil samples, and all hydraulic and electrical data, to Joliet. The service contact and address is shown below.

5) If the pump input pressure and the park brake output pressure are within the specified ranges shown in Table 2, visually inspect the park brake mechanism for the cause of the mechanical malfunction.

Park Brake Fails to Engage

6) With the park brake control in the cab in the "ENGAGED" position, measure the pump input pressure and the park brake output pressure of the park brake control valve. If the park brake output pressure is not within the specified range shown in Table 2, disconnect the electrical connector leading to the coil.

If the park brake output pressure then falls below the specified range shown in Table 2 for the 'Park Brake Output Pressure - Engaged' and the brake engages, the cause of the failure can be attributed to either a problem with the electrical harness, or a software malfunction.

7) If the park brake output pressure is not within the specified range shown in Table 2 for the 'Park Brake Output Pressure - Engaged', after the electrical connector has been disconnected, perform the following steps:

a) Shut down the machine, and turn off the engine.

b) Purge the pressure in the brake system.

c) Remove and thoroughly clean the cartridge valve.

d) Install the cartridge valve and retest.

8) If the pump input pressure and the park brake output pressure are still not within the specified ranges shown in Table 2, replace the cartridge valve by performing the operation described in Step 3).

9) When replacing the cartridge valve, take a sample of the oil from the pump and a sample of the oil returning from the park brake.

Notify Service Engineering and return the cartridge valve, both oil samples, and all hydraulic and electrical data, to Joliet. The service contact and address is shown below.

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