First, check that the brakes don't move and see if the barometer drops. If it is dropped, the cup is rotten and the cup or cylinder assembly needs to be replaced. If it does not descend, adjust the brake. If the cylinder clearance is too large, it will bleed quickly. It means there is air leakage. Suggest finding a place to check the car.

What is the reason why the air pressure disappears quickly when you step on the brakes?

Brake air pressure:

1. The air source of the brake valve is insufficient, because the cylinder of the vehicle cannot store enough compressed air; The air leakage of the brake valve pipeline and the blockage of the air path will cause insufficient compressed air pressure generated by the brake system during braking.

2. During pneumatic braking, the driver steps on the brake pedal, and the brake control valve opens, so that the channel between the air reservoir and the brake air chamber is communicated, so that the compressed air in the air reservoir enters the brake air chamber through the brake control valve, and enough air pressure pushes the brake air chamber push rod to extend outwards, driving the brake adjusting arm to rotate the cam, and the cam rotates and opens to press the brake shoe on the brake drum, thereby braking the wheel. Any of the above conditions may cause the pressure delivered to the brake chamber to drop. If the pressure is insufficient, the push rod of the air chamber cannot be pushed out, so that the brake shoe opens and presses on the brake drum to brake the wheel.

3. Air braking is a kind of braking method. A series of special devices used to make the outside world exert a certain force on some parts of the car, so that it can brake to a certain extent are collectively called braking systems.