What Causes the Friction Noise When the Car is Cold but Disappears When Warm?

[Briella]

There are several reasons why a car may produce friction noises when cold but the sounds disappear when warm, including issues with the generator belt or fuel pump failure. The specific causes are as follows: Generator Belt Issues: When the car is cold (including during a cold start), the noise from the belt can play a significant role in the overall vehicle noise. If the belt becomes loose and slips severely, it may produce a noticeable grinding sound. Additionally, the belt tends to be harder at low temperatures, which can result in a squeaking noise. However, at higher temperatures, the belt's improved elasticity reduces friction noise. Fuel Pump Failure: A "squeaking" sound similar to an electric current when the car is cold, after ruling out noise caused by belt or fuel line resonance, may indicate a fuel pump failure. A faulty fuel pump can lead to low fuel pressure and poor atomization from the injectors, resulting in an imbalanced air-fuel mixture and incomplete combustion.