What is the reason why the engine of large trucks makes abnormal noise?

1, the cam is excessively worn and the tappet jumps during operation.

2. The valve stem end and the adjusting screw or rocker arm are worn or improperly adjusted, resulting in excessive valve clearance, which leads to the collision between the side valve tappet end and the adjusting screw.

3. The valve tappet fixing nut is loose or the end face of the adjusting bolt is uneven.

4. valve spring retainer falls off.

5. There is too much carbon deposit in the valve guide and the valve is stuck.

Abnormal sound of valve:

When the engine is idling, it makes a continuous and rhythmic "click, click, click" (at the valve seat) or "bang, bang, bang" (at the valve seat); When the rotating speed increases, the noise will also increase, the temperature changes, and the single cylinder shuts down, and the noise will not weaken. If several valves are ringing, the sound will be chaotic. Valve foot sound and valve seating sound are collectively called valve sound.