Why does the brake make noise when the car is cold but the noise disappears when the car is warm?
2 Answers
Reasons for brake noise when the car is cold but the noise disappears when the car is warm are as follows: 1. The brake caliper does not return to its original position, or the oil settles when the car is cold, leading to this situation. 2. It may be due to the generator belt being too tight when the car is cold, or slight wear on the bearings of the water pump pulley or generator pulley causing noise, or belt slippage leading to noise. 3. When the engine starts cold, there is insufficient lubrication between the piston and the cylinder wall, or the clearance between the piston and the cylinder wall is too large, or the cylindricity of the piston is too large, causing the piston to swing and strike the cylinder wall under the pressure of high-pressure gas during the power stroke, resulting in a metal knocking sound. 4. The piston pin and connecting rod are too tight, or there is no lubricating oil between the piston, piston ring, and cylinder wall, causing high resistance and leading to this situation.
I've driven for fifteen years and encountered many brake noise issues. A 'squeaking' sound when starting with a cold car that disappears after driving for a while is mostly caused by dew or moisture condensation on the brake discs. This is especially common in northern winters; if the parking spot is damp, a thin frost can form on the metal surface, causing friction noise during the first few brakes. Don't worry too much as long as the sound disappears after the car warms up and the braking is normal. Of course, keep an eye out: if there are deep grooves on the disc surface or the brake pads have worn down to the warning tabs, the noise will persist regardless of temperature, and it's time to replace the parts. Avoiding parking near leaky spots like fire hydrants can save you some trouble.
