What is the reason for the valves being quiet when cold but noisy when hot?

[LaLayla]

The reason for the valves being quiet when cold but noisy when hot is: If the valves are noisy when the engine is hot, this indicates that there is clearance in the valves. It is necessary to check whether the engine oil is insufficient. If the engine oil level is normal, then the valves need to be replaced. During cold starts, due to the high viscosity and poor fluidity of the engine oil, there may be operational noise in the short term, and slight sounds may occur when the moving parts come into contact. This situation is normal and there is no need to worry. A cold start refers to starting the engine when the car has been parked for a long time and the car's temperature is the same as the ambient temperature. Many car owners hear a clicking abnormal noise from the engine compartment during cold starts. This noise sounds very abnormal, unlike the performance of a car running normally.