The brake system is absolutely necessary for the safe operation of a vehicle. If a vehicle's brake system isn't functioning properly the driver may not be able to stop the vehicle in time to avoid other vehicles or obstacles. It is understandable that some drivers are concerned when any noise comes from their vehicle's brakes. Sometimes the source of the noise is harmless but other times it is a symptom of a serious problem with the brake system.
New Pads
Sometimes when new brake pads are installed on a vehicle they make noise. After the car is used with the new brake pads for a few weeks, the noise from the new pads diminishes until it completely disappears. Noise from new brake pads occurs mostly with pads made from harder materials.
Temperature
Especially with metallic brake pads, the outside temperature can cause brake squeal. This brake squeal occurs mostly when the weather is cold and a little damp, such as on a cold winter's morning. As the vehicle is driven and the brakes are used on and off, the brake pads heat up and the noise disappears.
Warning Indicator
Some brake pads are equipped with a warning indicator built into the pad. A thin piece of metal is placed in the pad at the point where the pad is worn down enough it needs to be replaced. The thin piece of metal will contact the metal brake disc and create a squealing noise each time the vehicle's brakes are applied. This squeal is to let the driver know the brake pads have worn down to the point they need to be replaced. Drum brakes may also make a sound when the brake shoes need to be replaced, but the sound is not a squeal, but more of a low-pitch hum or moan.
Problems
Brake noise can also signal a problem with a vehicle's brake system. Many factors can cause noise to come from a vehicle's brakes. Brake discs that are cracked from the heat of braking or have a rough surface can cause brake noises. If the brake discs simply have an uneven surface they may be able to be refinished, where some of the surface is shaved off to make the disc smooth again. If the disc is cracked it should be replaced to avoid brake system failure. Brake noise can also be caused by loose brake pads. With either type of brakes, a grinding noise is a sign of metal-on-metal contact between the brake shoes and drum or pads and rotor, meaning the shoes or pads are worn completely away and must be replaced.
Warning
If you hear an unusual sound coming from your brakes, have your vehicle checked by a qualified mechanic immediately.
