What Causes Brake Noise When Starting the Car in the Morning?
2 Answers
If the car has been parked for a long time, especially overnight, and produces abnormal noise when braking after starting, but the noise disappears after driving for a while, this is due to high air humidity and moisture on the brake pads, which can be ignored. If abnormal noise occurs every time you brake, it is caused by severe wear of the brake pads. There are three situations of brake noise: the alarm shim will emit a sharp abnormal sound to prompt replacement; the brake disc is severely worn and produces abnormal noise; a sharp and piercing sound is emitted when braking. The alarm shim will emit a sharp abnormal sound to prompt replacement: Usually, the vehicle's braking system has its own alarm system to warn the owner to replace the brake pads. When the brake pad wear exceeds the specified alarm value, the alarm shim will emit a harsh noise to remind the owner to go to the repair shop for inspection or replacement of new brake pads. If not replaced in time, the metal alarm shim will carve a fatal groove on the brake disc, causing the brake disc to be scrapped. At the same time, brake pad wear to the limit may lead to brake failure, resulting in serious traffic accidents. The brake disc is severely worn and produces abnormal noise: If the brake disc is severely worn, the outer edge where the brake disc and brake pads do not rub will become a raised ring relative to the friction surface. At this time, if the corner of the brake pad rubs against the raised outer edge of the brake disc, abnormal noise may occur. There are generally two ways to solve this situation. One is to go to the repair shop to grind the edge of the brake pad to avoid the raised edge of the brake disc and prevent friction; the other is to directly choose to replace the brake disc. A sharp and piercing sound is emitted when braking: When a new car emits a sharp and piercing sound when braking, many owners think it must be a quality problem with the vehicle. In fact, this is not the case. New brake pads and brake discs require a running-in process. When braking, if it happens to rub against a hard point on the brake pad (due to the material of the brake pad), this kind of abnormal noise will be emitted. You can go to the repair shop to apply some lubricating oil to reduce the noise.
I've repaired quite a few cars, and the most common cause of brake noise during morning startup is rust or moisture on the brake rotors and pads. For instance, after nighttime rain or heavy dew, moisture can cause rust to form on metal surfaces, resulting in a sharp squeaking or grinding noise when you first apply the brakes in the morning. It might feel alarming, but it's usually a temporary issue and nothing to worry about. Another possible reason is severely worn or aged brake pads, where the metal backing is exposed, making the noise more pronounced during friction. Additionally, dust or debris trapped in the brake calipers can cause noise, especially in the early morning when temperatures are low and materials contract, leading to greater variations in friction coefficients. In such cases, I'd recommend avoiding high-speed driving initially—instead, drive gently for a while to let the brake rotors warm up, and the noise should fade. However, if this happens every day or the noise grows louder, it's crucial to check the brake pad thickness immediately, as they might be too thin and require replacement or cleaning. By the way, parking location matters too—avoiding waterlogged areas or spots with high humidity can help prevent such issues. Regular maintenance checks on the brake system can save a lot of hassle down the road.
