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Fixing Brake Squeal, Noise

Brake disc - rotor

Your brakes are the most important safety item on your car and when they start making noise or acting funny, you are right to feel worried. We've talked about brake pulling and how brake calipers work before (click here), but what about when they're just making noise?

Sometimes, brake squeal is due to the pads being worn and requiring replacement. Anytime a brake squeal or other noise becomes persistent, you should quickly inspect them for problems.

Brake Inspection

Check the brake fluid level and how it looks. It should be at the "full" mark and should be the dark color of used motor oil. If neither is the case, you have a problem.

Start the engine with the brake pedal pushed in. If the pedal's pressure changes when the engine is running, that's a good sign. If the pedal does not drop in slightly when the engine starts or if it feels "spongy" or loose, you have a problem.

Remove each wheel in turn and inspect the brake pads, linings, rotor/drum, calipers, etc. You're looking for worn pads, loose linings, worn or uneven rotor or drum surfaces, leaking calipers, etc. Anything that looks wrong probably is. Check everything.

Diagnosing Disc Brake Squeal

If the squealing is not because the brake pad's indicator has begun contacting the rotor to make the tell-tale "screech" that says your pads need repalcement, then something else is the issue. Inspect the rotors closely. Are they irregular or "bumpy?" These irregularities cause the brakes to chatter and sometimes squeal as the metallic pads come in contact with them.

If the rotor's surfaces are uneven, you should have them resurfaced or replace them. This usually fixes the problem. Also inspect for loose brake pads and misaligned calipers.

Drum Brake Noise

Drum brakes can make noise for the same reason disc brakes do. Most often it's an uneven contact between the shoe and the drum, usually because the springs are mis-aligned, broken, or the drum's surface is uneven. Sometimes, the springs holding the shoes in place can break or come loose, causing them to rattle around inside the drum potentially wreaking havoc.

The most common problem, though, is misalignment of the drum and shoe. Back before asbestos pads, mechanics often shaped shoes to fit the drum more precisely, similar to how a farrier fits a shoe to a horse. Today, that's a lost art, though with asbestos pads being a thing of the past, it could make a comeback. It's being seen in automotive racing today as precision pads are milled to their discs.

For the home mechanic, if a shoe is wearing unevenly, mostly towards the middle rather than the edges, replacement of the shoe with one that fits properly is the best fix. The drum should also be inspected and "rolled" to check for balance and wobble. A wobbling drum is warped and likely should be replaced.

Other Fixes To Try

If you cannot find the exact problem, you may be able to narrow it down by doing some quick fixes that may help.

Try lubricating the calipers and cleaning out the drums and cleaning off the rotors. Use brake cleaner to get any residue and dust out of the drum and off the discs. Some calipers have lubrication points where axle grease is applied to help them move during braking.

If no lubrication points are present, try replacing the slides, pins, and bushings on the caliper(s).

Finally, of course, replacing the pads or shoes may repair the problem without any further fuss. If you keep a new set ready for use as part of your maintenance regimen, it doesn't hurt to install them and see if the problem goes away.