Brake Noise Solutions
Most brake noise complaints are squeak-related or metal-on-metal are related to the brake pad. The grinding noise is the result of worn pads contacting the rotor and is a common problem. The least common noise is a knocking sound.
Brake Squeaking Solution
Brake squeaking usually occurs after servicing and is easiest just to prevent it rather than fix it. Brakes are located in a hostile environment with lots of rust and corrosion. When removing the pads look for uneven wear, and restricted movement. This indicates that the load isn’t evenly distributed and that pads are probably hanging up. Continue the system inspection by opening the bleeder valve and push back the piston on the calipers. Use a C-clamp between the outer pad and the back of the caliper. Retracting the piston and moving the caliper away from the outer pad should take minimal effort, but if this takes excessive effort, don’t force it. Look for what’s binding and remove the caliper. If the slides are frozen, the piston should retract easily with the caliper removed. lubricate and service the sliders and carrier and be sure to remove the anti-rattle hardware to clean rust. The rust binds the pads and causes noise and poor performance. Squeaks happen when the pads vibrate against the piston and bracket when the brakes are partially applied. When reinstalling the pads, add brake lube between the shims and pads if possible. Cars with drum brakes make a grinding noise when not driven for prolonged amounts of time. This goes away with driving, but only takes a quick cleaning and visual inspection to fix. During drum inspection, check for bad hardware and excessive rust build up on the drums. The rust can be cleaned away but it is often more cost effective to just replace the brake drums.
The knocking noise mentioned earlier is caused by the brake pads rattling in the brackets. This diagnosis is easy and can bee performed on the initial road test. Lightly apply pressure to the brakes while going over a potholed road. If the noise is gone, the pads are moving. To fix the rattling pads, buy a hardware kit with the parts needed.