What are the causes of the looseness of the valve seat ring of an automobile engine and how to repair it

The valve seat is easy to loose and fall off because of overloading, overspeed running, excessive heat load, small interference basin, or improper technology in maintenance.

When the new valve seat is installed, the bearing hole of the seat ring should be measured, according to the actual diameter of the seat ring selection, otherwise blindly hit the new seat ring seat hole, because the interference is small and fall off. Sometimes the interference fit is not suitable, but the roughness of the fit surface is not suitable, so the interference fit is small, which is also the main reason of the looseness.

 the use of the car to regular maintenance and inspection, found that the seat ring loose and timely replacement. The old seat ring can be pulled out with a pull tool or put out on the machine tool. When the roundness error of the seat ring hole exceeds 0.04 mm, it should be repaired by enamel. The Surface roughness after enamel should meet the requirements. The valve seat should be made of the original parts as far as possible. The Surface roughness after the blank processing should meet the requirements and the roundness error should not be greater than 0.03 mm. The seat holder is placed in the seat hole after fully cooling in the liquid nitrogen. The seat holder is pressed into the seat hole by a punch with a centering rod. In the case of no liquid nitrogen cooling equipment, the cylinder head can be evenly and slowly heated to about 150 ° C, and then the seat ring is pressed into the seat ring hole.