5-2 Lower Mechanism: Travel Drive Unit [2] Troubleshooting for parking brake Trouble Description While the motor is stopped with an external load on it, the motor rotates.
Motor drive force is not delivered. The motor section is abnormally hot.
Possible Cause
Countermeasure and Solution
A worn disk reduces the torque of the parking brake.
Disassemble the unit to replace the parking brake disk. Clean the part, and re-assemble the unit.
Contact defect or other problem deteriorates the disk surface and reduces the parking brake torque.
Disassemble the unit to replace the disk. In addition, repair the surface of the counterpart of the disk and re-assemble the unit.
A fatigued or damaged spring reduces the parking brake torque.
Disassemble the unit to replace the spring. Clean the part, and re-assemble the unit.
The external load is too much for the parking brake capacity.
Review the external load and correct the value.
A damaged O-ring causes the pressurized oil to escape and the parking brake cannot be released.
Disassemble the unit to replace the Oring. Clean the part, and re-assemble the unit.
A clogged orifice of the oil path for parking brake release prevents the pressurized oil from entering to the parking brake cylinder chamber and the parking brake cannot be released.
Disassemble the unit to remove the foreign matter in the orifice. Clean the part, and re-assemble the unit. In addition, flush inside the pipe.
A clogged or long and narrow drain pipe rises the drain pressure and the parking brake cannot be released.
Clean the drain pipe. In addition, review the piping system and reduce the pipe line resistance.
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