Brake squeal by itself is not a serious problem, but it can be symptomatic of a problem that, if left unattended, could develop into a much larger issue. Squealing brakes are also annoying for the driver, the vehicle passengers, and any nearby pedestrians. Diagnosing the brake squeal is the first step in eliminating the underlying cause.
Instructions
- 1
Determine if the brake noise is constant or only audible when the brakes are applied. Identify if the noise has always been there or has slowly developed over time. Consider if the noise started suddenly and, if so, whether it was after a brake servicing. Make a list of everything you know about the problem to help in the diagnosis.
2Wait for new pads and shoes to wear in. If the brakes have been recently serviced it will take about 300 to 400 miles of city driving before any new pads and shoes wear in with the rotors, and a tolerable amount of noise during this period is not unexpected. If the squeal does not go away during this period, it is possible that the problem lies in the brake pad or shoe linings. Some linings are made with harder material than others, and brake squeal is elevated when harder linings are used. Replacing the pads or shoes with ones that have a softer lining material may make the noise go away.
3Check disc brake pads to see if they are fitted with soft noise-dampening shims. Lower cost pads often come with lower quality shims, and if these are replaced with high quality shims the squeal will often be reduced or eliminated. If no shims are present then installing high quality shims will likely resolve the issue.
4Check that disc brake pads are not worn out. Many pads incorporate a looped metal leaf wear indicator that will rub on the disc when the pad reaches minimum thickness. This produces a loud metallic squeal to audibly warn the driver that the pads are nearly worn out. Wear indicators are normally found on the inside pads only. Replacing worn-out pads will solve this problem.
5Inspect the pad and shoe linings to see if they are damaged or unevenly worn. Uneven lining wear can result in uneven pressure against the rotor, sometimes causing a squeal during braking. For disc brakes this is normally the result of a seized caliper. In this case, the caliper guide bolts should be thoroughly lubricated and new disc pads installed. On drum brakes this normally means that the shoe hold-down pins are bent or damaged, in which case the brake should be fitted with new shoes and hold-down pins.
6Examine the parking brake. If there is a continuous faint squeaking or squealing from one or both of the rear wheels while the car is moving, and the sound disappears when the brakes are applied, then it is possible that the parking brake is stuck in a partially applied position. Check for proper operation of the parking brake handle or pedal and be sure that it is releasing properly. Check the cable at either the handle or pedal end in the passenger compartment and at the brake end at the rear wheels and look for signs of rust or corrosion. Corroded cables should be replaced.
