A Yutong Heavy Industry GJT112 bulldozer suddenly appeared automatic deviation during the operation. The operator immediately stopped and contacted professional maintenance personnel to arrive. After careful inspection and analysis, the cause of the failure phenomenon may occur in the following parts:

1: The brake pads are severely worn

2: The return spring of the brake pad falls off

3: Steering gear failure or oil pipe leakage

4: The left and right air pressures of the bulldozer wheels are inconsistent

5: One side brake piston stuck

Since there is no abnormality in the steering and braking system during automatic deviation: the brake pad failure can be eliminated, the bulldozer can be started, and the steering gear can be carefully checked. The steering is very flexible and there is no abnormality in the automatic steering. The steering gear works normally.

In addition, the left and right tire pressures of the bulldozer were measured, and they were all within the normal range and the left and right tire pressures were basically the same. However, the temperature of the right brake disc was found to be high during the tire pressure measurement, and it was suspected that the right brake disc was faulty.

The GJT112 bulldozer adopts an air-push oil disc brake system. A brake cylinder is installed on the disc brake. When the brake pedal is stepped on, the high-pressure gas from the air compressor pushes the gas piston of the gas-liquid master cylinder, and the gas piston pushes the oil piston. The brake fluid enters the brake cylinder piston chamber of the disc brake through the oil pipe and pushes the piston to extend. The piston drives the friction plate to clamp the brake disc and brake the wheels.

There are 4 possibilities for the brake cylinder on the disc brake to fail to return:

1: The exhaust port of the foot brake valve is blocked, and the high-pressure gas cannot be discharged into the atmosphere, causing the spring of the gas-liquid master cylinder to fail to return, causing the brake oil to top the brake cylinder piston of the disc brake and fail to return. . 2: The tubing from the gas-liquid master cylinder to the disc brake is blocked, causing the brake cylinder piston to not return.

3: The spring of the gas-liquid master cylinder itself cannot return: the brake fluid cannot return to the oil storage chamber of the gas-liquid master cylinder under the action of high-pressure gas, causing the brake cylinder piston to not return.

4: The piston of the disc brake cylinder cannot be returned due to the dirty brake fluid or the rusty piston.

When analyzing the fault, first stepped on the foot brake valve, and heard the exhaust sound after releasing the pedal, which ruled out the first possibility. Then, unscrewed the oil pipe joint from the gas-liquid master cylinder to the disc brake cylinder, stepped on the foot brake valve several times, and found that the joint was sprayed with brake fluid and there was a large pressure.

The reason for the failure should be that the disc brake cylinder piston cannot be returned due to dirty brake fluid or rusty piston. Open the brake disc immediately and find that the brake piston is stuck, which causes the brake friction lining to fail to return, and the brake disc is compressed and heated. Then remove the caliper brake disc, replace the brake piston and dust cover, remove the air in the brake system, and then troubleshoot.