Reasons and precautions for abnormal sound when the hand brake valves leaks and brakes
1. Air leakage of hand brake valve
When the hand brake valve is set to the "parking brake" position, the hand brake valve continues to leak air from the exhaust port. There is foreign matter, or the seal of the intake valve is damaged. Replacing the intake valve seal with a repair kit solved it.
During parking braking, air leakage from the handbrake valve will not cause other failures. However, when the handle of the handbrake valve is set to the "driving" position, the handbrake valve leaks air, which will cause the (middle) rear axle wheel to "tighten" when the car is running. This is generally due to the handbrake valve. The valve stem is not tightly closed due to the contact between the valve stem and the air valve. Obviously, the reason for the poor sealing of the exhaust port may be the damage to the seal or the separation of foreign matter or oil between valve stem 7 and air valve 10. The exhaust port is not tightly closed. Disassemble and clean or replace the seal of the intake valve, and the fault can be eliminated.
2. The charging time of the hand brake air reservoir is too long
Before the car starts, the main brake air cylinder should be fully air-pressured first. The warning light goes out and the buzzer stops, indicating that the main brake (front brake air cylinder and (middle) rear brake air cylinder) has sufficient pressure. When the low air pressure warning light is on, it means that the air pressure of the hand brake air cylinder is insufficient, and the spring brake sub-chamber has not completely released the brake. At this time, if the car starts forcibly, the (middle) rear axle will have the phenomenon of brake "tightening". Therefore, the car can start only after the warning light goes out.
Under normal circumstances, after the main brake air reservoir is full of air (after the main brake low-pressure warning light goes out), the hand brake air reservoir will be full soon (the hand brake low-pressure warning light goes out). If this charging time is too long (the hand brake low-pressure warning light does not go out for a long time), it means that the gate valve (or overflow valve) connected between the (middle) rear brake circuit and the hand brake circuit has a problem. question. The gate valve is a one-way relief valve. When the air pressure of the (middle) rear brake circuit reaches 6.5 bar, the valve should be opened to quickly charge the hand brake circuit. If the pressure value is adjusted too high and it is stuck (or frozen) and not opened at all, it will cause the fault of the handbrake circuit to be charged too long. Disassemble and adjust the valve to eliminate the problem.
3. Air leakage in the spring energy storage chamber
Damaged or strained piston seals of spring energy storage compartments, or strains of compartmented cylinders, etc., will cause air leakage in the compartments. Because the spring energy storage and braking sub-chambers of the (middle) rear axle wheels are connected by air, as long as there is air leakage in one sub-chamber, the air pressure of each sub-chamber will drop to the bottom, thus causing the (middle) rear axle wheels when driving. The result of "tighten up". In the event of such a fault, the leaking brake sub-chamber needs to be checked and repaired. The removal and installation of the spring energy storage brake sub-chamber must be carried out on the press to ensure safety.
4. Air leakage of hand brake relay valve
When the car is in the parking brake condition, the relay valve leaks air, which will not cause any trouble to the car. This is obviously because the intake valve seal of the brake valve is damaged or there are foreign objects or impurities between the valve and the valve seat, causing The valve is not tightly close.
When the car is in the driving state, the relay valve continues to leak air from the exhaust port. Obviously, the exhaust valve and the piston are not tightly closed. At this time, the air pressure in the spring energy storage brake chamber will be insufficient, resulting in the "tightening of the service brake". "failure.
To learn more, please refer to: Automotive Brake Master Cylinders Manufacturer