Common faults of semi-trailer head and their solutions

Common faults and solutions for semi-trailer heads are here:

First, when the tractor pulls the valve or steps on the foot brake, if there is a leak at the exhaust port of the emergency relay valve, just replace the relay valve repair kit. Because the leakage of the relay valve will cause the drag brake problem.

Next, let’s talk about the connection between the tractor and the semi-trailer. Before connecting, it is necessary to check whether the traction height, traction pin size, front slewing radius and clearance radius of the semi-trailer match the tractor. At the same time, carefully check whether there is sand, dust or other foreign matter on the working surface of the tractor saddle and the semi-trailer traction pin and traction slide plate, and ensure that there is enough lubricating grease. When adjusting the support legs, the traction slide plate of the semi-trailer should be 10 to 30 mm lower than the center position of the plane on the traction saddle of the tractor. Then, operate the traction seat locking mechanism to open the locking block. When the tractor is backing up, the center line should be consistent and the offset should be controlled within 40 mm. The angle should be less than or equal to 5° when fully loaded and less than or equal to 7° when unloaded. Check whether the towing seat locking block has correctly locked the towing pin, and move the towing vehicle forward slightly to check the connection.

In terms of air line connection, just connect the two air pipe joints on the towing vehicle to the semi-trailer. If the air pressure is lower than 0.7MPa for a long time, or there is obvious drag brake phenomenon during the driving of the trailer, the fault of the towing vehicle should be eliminated first, and then the source of the air leakage should be found by applying soapy water, and various possible faults should be eliminated. For example, “leakage at the handshake connection”, “leakage at the pipeline joint”, “cross-breathing of the brake air chamber”, “leakage of the emergency relay valve” and “leakage of the trailer ABS valve”. If there is still air leakage, check whether the valve body has water or rust, and the valve body may need to be replaced.

The reasons for the head jumping when the semi-trailer starts may include unstable throttle pedaling, and the throttle should be increased when starting; the amplitude of the truck clutch is not mastered well, and the throttle should be increased and the clutch should be slowly stepped on to release the clutch when starting; there is a problem with the truck pressure plate; when starting with heavy load, the usual method of slowly releasing the clutch and quickly refueling may cause the trailer head to jump up. If the vehicle jumps, it may be due to insufficient horsepower or clutch problems, such as incomplete separation and severe wear of the pressure plate. If you encounter a jump problem, you should check the clutch, horsepower and operation in time, and consult a professional technician if necessary.