The abnormal sound of the piston ring mainly includes the metal knocking sound of the piston ring, the leakage sound of the piston ring and the abnormal sound caused by excessive carbon deposition.

(1) The metal knocking sound of the piston ring.
After the engine works for a long time, the cylinder wall is worn, but the place where the upper part of the cylinder wall is not in contact with the piston ring almost maintains the original geometry and size, which makes the cylinder wall generate a step. If the old cylinder head gasket or the new cylinder head gasket replaced is too thin, the working piston ring will collide with the cylinder wall step, making a dull "pop" metal bump. If the engine speed increases, the abnormal noise will also increase. In addition, if the piston ring is broken or the gap between the piston ring and the ring groove is too large, it will also cause a large knocking sound.

(2) The sound of air leakage of the piston ring.
The elastic force of the piston ring is weakened, the opening gap is too large or the openings overlap, and the cylinder wall has a groove, etc., which will cause the piston ring to leak. The sound is a "drinking" or "hissing" sound, or a "popping" sound when there is a severe air leak. The diagnosis method is to turn off the engine when the water temperature of the engine reaches above 80 ℃. At this time, you can inject a little fresh and clean oil into the cylinder, crank the crankshaft for a few turns, and then restart the engine. If it appears, it can be concluded that the piston ring is leaking. Attention: Automobile Inspection and Maintenance Major

(3) Abnormal noise due to excessive carbon deposition.
When there is too much carbon deposition, the abnormal noise in the cylinder is a sharp sound. Because the carbon deposition is burned red, the engine has symptoms of premature ignition, and it is not easy to turn off. The formation of carbon deposits on the piston ring is mainly due to the lack of tight sealing between the piston ring and the cylinder wall, the excessive opening gap, the reverse installation of the piston ring, and the overlapping of the ring ports, etc. The ring part burns, resulting in the formation of carbon deposits or even sticking to the piston ring, causing the piston ring to lose its elasticity and sealing effect. Generally, this fault can be eliminated after replacing the piston rings with suitable specifications.