Camshaft can cause abnormal wear clearance between the cam shaft and the bearing increases, the axial displacement occurs when the camshaft movement, resulting in abnormal sound. Abnormal wear can also lead to a gap between the drive cam and hydraulic tappet increases, impact occurs when a hydraulic tappet cam and combine to produce abnormal sound.

1) when the engine speed operation sound obvious, there blunt heavy "despair, despair" sound, can be heard at idle, when high-speed operation, it seems to disappear.

2) as a single-cylinder off the fire test, the sound change.

3) When the camshaft bearing rattling nearby with a vibration.