1. Leakage of the hand brake valve
During the parking brake, the air leakage of the hand brake valve will not cause other failures. However, when the handbrake valve handle is set to the "driving" position, the handbrake valve will leak air, which will cause the rear axle wheel to "tighten" when the car is running (in the middle). This is generally due to the handbrake valve The valve stem and the air valve are not tightly closed. Obviously, the cause of the air exhaust opening 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 sealed. Disassemble and clean or replace the intake valve seal, and the fault can be eliminated.
2. The inflation time of the hand brake air reservoir is too long
Before the car starts, the main brake cylinder should be fully inflated first. The warning light goes out and the buzzer stops, indicating that the main brake (front brake cylinder and (middle) rear brake cylinder) has sufficient pressure. If the low air pressure warning light is on, it means that the air pressure of the hand brake cylinder is insufficient, and the spring brake compartment has not fully released the brake. If the car is forced to start at this time, the (middle) rear axle will have a phenomenon of "tightening" of the brakes. Therefore, the car can start after the warning light goes out.
Under normal circumstances, after the main brake air tank is fully inflated (after the main brake low-pressure warning light goes out), the hand brake air tank will be sufficient soon (the hand brake low-pressure warning light goes out). If the inflation time is too long (the hand brake low air 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 is faulty. question. The gate valve is a one-way relief valve. When the (middle) rear brake circuit pressure reaches 6.5 bar, the valve should be opened to quickly inflate the hand brake circuit. If the pressure value is adjusted too high and is stuck (or frozen) and does not open at all, it will cause a failure of the hand brake circuit to be inflated for too long. Disassemble and adjust the valve to eliminate the fault.
3. Air leakage in the spring energy storage compartment
The damage and strain of the spring energy storage sub-chamber piston sealing ring, the sub-chamber cylinder strain, etc. will cause the sub-chamber air leakage. Because the spring energy storage brake sub-chambers of the (middle) rear axle wheels are all connected by air passages, so as long as there is an air leak in one sub-chamber, the air pressure of each sub-chamber will drop to the bottom, thus causing the (middle) rear axle wheels to The result of "tightening". In case of such a failure, the leaking brake chamber needs to be disassembled and repaired. The disassembly and installation of the spring energy storage brake compartment must be carried out on a press to ensure safety.
4. Leakage of hand brake relay valve
When the car is in the parking braking condition, the relay valve leaks air, which will not cause trouble to the car. This is obviously due to damage to the intake valve seal of the brake valve or foreign objects or impurities between the valve and the valve seat, causing the valve is not closed tightly.
When the car is running, 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 compartment will be insufficient, resulting in "tightening" of the driving brake. "failure.
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