Why Does the Car Make Noise When Braking Cold?
3 Answers
Car cold braking noise may be caused by the brake vacuum booster, which is a common phenomenon in most vehicles and does not affect driving safety. If the noise is too loud, the brake vacuum booster can be replaced. The working principle of the brake vacuum booster is as follows: 1. Start the engine. When the engine is in the intake stroke, the vacuum degree in the intake manifold is greater than that in the rear chamber of the vacuum booster, and the vacuum damping valve opens at this time. 2. The engine draws air from the rear chamber through the intake manifold into the engine via the vacuum damping valve. When the vacuum degree in the rear chamber exceeds that in the intake manifold, the vacuum damping valve closes, creating a vacuum and negative pressure in the rear chamber. 3. When the brake pedal is pressed, the one-way valve inside the vacuum booster closes, and the pressure relief valve opens, allowing air to enter the front chamber of the vacuum booster through the pressure relief valve, creating positive pressure. Since the pressure in the front chamber is greater than that in the rear chamber, a pressure difference is generated. 4. Under the positive pressure in the front chamber, the diaphragm is pushed toward the rear chamber, overcoming the return spring force of the pressure plate, and the push rod of the brake master cylinder is pushed, driving the first-stage piston of the brake master cylinder to generate vacuum assistance.
Every time I drive out in winter, the car squeaks when braking after sitting overnight, and I'm no longer surprised by it. It's mainly due to condensation or rust on the brake discs in low temperatures, especially common after rain or in humid environments. The initial braking causes friction points to emit a sharp sound. After driving a few meters, the friction heats up and the moisture evaporates, making the noise disappear naturally. This isn't a major malfunction; my old car has been like this for over a decade. However, I remind myself to regularly check the wear level of the brake pads to avoid debris buildup. If the sound persists for a long time or becomes louder, it indicates that the braking system may be severely worn, and it's time for a maintenance check at the repair shop to ensure safe driving. Don't overlook these small details—safety comes first when driving.
As someone with a passing interest in cars, I've pondered why cold brakes squeak. The reason lies in the contraction of metal brake discs at low temperatures, which increases surface gaps, allowing rainwater or moisture to seep in and cause oxidation and rust, resulting in noise during friction. This is especially noticeable in cars with harder disc materials during cold weather. Lightly applying the brakes a few times after starting warms up the disc surface, eliminating the noise. Parking away from puddles can reduce occurrences. Long-term neglect may allow impurities to damage the system, so it's recommended to quickly clean the brake discs once a week to prevent rust. This knowledge has saved me unnecessary repair costs.
