Improper ring assembly technology is easy to cause the valve seat ring to loosen and fall off.
When replacing a new valve seat, the bearing hole of the seat ring should be measured, and the seat ring should be selected according to the actual aperture, otherwise the new seat ring will blindly hit the seat ring hole and fall off due to the small interference. Sometimes, although the fit interference meets the requirements, the roughness of the mating surface is not suitable, resulting in a small actual interference, which is also the main reason for looseness. Dongfeng EQ6 100 engine assembly technical conditions stipulate that the interference is 0.053-0. 1 1 mm, and to prevent the seat ring from loosening, the upper limit can be selected during assembly.
The car should be regularly maintained and inspected during use, and the seat ring should be replaced in time if it is loose. The old seat ring can be pulled out with a puller or lined on a machine tool. When the roundness error of the seat ring hole exceeds 0.04mm, it should be repaired by honing, and the surface roughness after honing should meet the requirements. The valve seat shall adopt original fittings as far as possible, and the surface roughness of the processed blank shall conform to the regulations, and the roundness error shall not be greater than 0.03 mm. Before installing the seat ring, it shall be fully cooled in liquid nitrogen, and then it shall be quickly put into the seat ring hole. Insert a punch with a centering rod into the valve guide and press the seat ring into the seat ring hole. Beating with a hammer is not allowed. Without liquid nitrogen cooling equipment, the cylinder head can be heated evenly and slowly to about 150℃, and then the seat ring can be pressed into the seat ring hole.