The characteristics of the connecting rod bearing noise are: the sound is obvious at medium speed, the noise is not obvious due to the increase of other mechanical noise at high speed, and the sound is weakened at idling speed. When the temperature of the diesel engine changes, the noise does not change. In the mid-speed range, when accelerating and decelerating, the noise will become louder as the speed increases. "cylinder-breaking method" test, the noise becomes smaller or disappears.