Auto Repair Help
JIM’S CORNER – AUTO REPAIR HELP

DIAGNOSE – BRAKES MAKE A GRINDING NOISE WHEN APPLIED
by Jim Miller

SYMPTOM SUMMARY
The brakes emit a grinding noise when applied. The braking action may not be as effective as normal.

USUAL CAUSE
This symptom is usually caused by metal to metal contact between the brake pad and rotor or brake shoe and drum. The brake pads and shoes have a metal surface that the friction surface is mated to. Once the friction material is worn off, the metal surface will contact the rotating surface of the drum or rotor. This metal to metal contact usually results in a grinding noise.

DIAGNOSIScheckengine
A visual inspection of the brake system will indicate the cause of the noise. The brake pads and rotors should be inspected for damage. If the rotor is excessively worn beyond the manufacturers minimum thickness, the rotor will have to be replaced. If the drums have grooves worn in them beyond the manufacturers maximum diameter, they will require replacement.

PRECAUTIONS, TIPS, and NOTES
When replacing the brake pads or shoes, it is recommended that the brake rotors and drums be machined (often referred to as surfaced or turned). This will provide a flat mating surface for the new pads or shoes which will prevent brake squeal. A high quality anti-squeak compound should be applied sparingly to the back side of the new pads. Some vehicles use metal shims between the pad and the caliper. These shims should be replaced or cleaned and re-installed. Brake rotors and drums become extremely hot after vehicle operation and braking. Use caution when working on the braking system. Brake rotors and drums have a manufacturers minimum thickness and maximum diameter specifications. Never machine a rotor or drum beyond the manufacturers specifications. The minimum thickness and maximum diameter specification is usually stamped on the brake rotor or drum.

(Jim is a lifelong fan of Dodger Baseball and used to race sprint cars in the 1980s.)

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