Phenomenon: When the car is moving, one or more feet are braked. The brake pedal is stepped to the end and the brake suddenly fails.

the reason:

1. There is no brake fluid in the main pump.

2. The main pump bowl is damaged or overturned.

3. The sub-pumps are damaged or overturned.

4. The brake pipe is severely broken or the joint is out of joint.

Diagnosis: The reason why the hydraulic brake system has a poor braking performance is generally based on the brake pedal stroke (commonly known as high and low), the soft and hard feeling when the brake pedal is depressed, the stability after depressing the brake pedal, and the brake When the pedal height increase to judge.

1. The pedal height is too low and brake performance is poor during normal braking. If two or more feet are braked consecutively, the pedal height is increased and the braking performance is improved, which means that the clearance between the brake drum and the friction plate or the master cylinder piston and the push rod is too large.

2. When the brake is maintained, if the height of the pedal is slowly or rapidly decreased, it indicates that the brake pipe is broken somewhere, the joint is tightly closed, or the bowl of the sub-tank is poorly sealed, the return spring is too soft or broken, or the total pump bowl , poor seal of the leather ring, defective oil return valve and oil valve. The brake pedal can be depressed first to observe the presence of brake fluid leakage. If the outside is normal, check the sub-pump or master pump for failure.

3. When several consecutive feet are braked, the pedal height is still too low, and after the second foot is braked, it feels that the master pump piston is not returning, and that the depression of the brake pedal is the sump stroke of the master cylinder and the piston. The main pump bowl cracked or the return spring was too soft.

4. The height of the pedal slightly increases with a few feet of continuous braking, and it has a sense of elasticity, which means that air has penetrated into the brake pipe.

5. A few feet in a row, the pedals were stepped to the end, and there was no reaction force on the pedals, indicating that the brake fluid in the main pump's reservoir was seriously depleted.

6. When the brake pedal is continuously braked, the pedal height is low and soft, and the plug of the plug of the fluid in the total oil inlet hole is blocked.

7. When one or two feet brake, the pedal height is appropriate, but too hard braking performance is poor. It should be checked whether the clearance between the friction plates and the drums is too small. If the clearance is normal, check the surface condition of the drum and the friction plate. If normal, check whether the brake shoe spring is too hard, whether the main pump or the sub-pump cup is swollen, and whether the piston and the cylinder wall are loose. If both are normal, you should check whether the brake hose is aging.