Abnormal noise of wheel loader and forklift diesel engine——piston knocking

The main reason for piston knocking of mini loaders is that the piston and the cylinder wall are worn out, the fit gap exceeds a certain limit. The piston swings during the up and down movement, knocking the cylinder wall and making noise. Sometimes, although the fit clearance does not exceed the limit, it will sound if the connecting rod is bent and deformed.
Piston knocking sound is obvious when the diesel engine temperature is low, and it is especially clear when idling. When the temperature rises, the noise will decrease or disappear. This is the characteristic of piston knocking.

Because of the similarities between the knocking sound and the piston pin sound, in order to facilitate the distinction, a small amount of oil can be injected into the top of the piston from the injector seat hole, and the diesel engine of the small loaders can be started again after rotating the crankshaft several times. If the sound disappears immediately after starting, it is a knocking sound. It should be noted that when the fuel supply is advanced (within the specified range), it will also cause a slight knocking sound, which is normal.