Knowledge of auto parts

Causes of brake noise and How to Fix Them

Common Brake Noises and Their Causes

Noise Possible Cause
Grinding Stop driving! Usually caused by the brake pad being worn down to nothing
Thumping from rear Hard to diagnose, but usually the rear drums
Squeaking Either cheap brake pads, or the brake wear indicator is hitting the rotor
Thumping or squealing If car is parked outdoors, probably caused by rusted rotors
Scraping You may have picked up a rock

Causes of brake noise and How to Fix Them

1. Grinding Noise When You Apply Your Brakes: A Wake-Up Call

Hearing a grinding noise when you apply your brakes is really like hitting a rumble strip on the edge of the highway; if you hear this, you need to wake up and stop driving. A grinding noise on braking is usually caused by a lack of brake pad material; the pads and rotors are now metal to metal, with no braking material left.
Brake pads are like bars of soap. Eventually they get used up, and you have to replace them and spend a little money.
If you don’t, and your brakes get to the point of grinding, just imagine dollar signs rising into the air every time you step on the brake pedal, even just a little. The grinding noise is just a little voice whispering in your ear saying, ”You’re killing me!” Mechanics have an acronym for this, it’s called CPR (calipers, pads, and rotors). And when you get the bill for your brake job, you will need CPR (cardio-pulmonary rescuscitation).
You are supposed to replace the pads so they don’t grind your rotors down to a tissue. If you replace your pads on time you can often keep your rotors.

2. Thumping Noise From the Rear When Braking

This brake issue is one that will annoy the hell out of the driver, and suck the life out of the technician. It took me months to figure out what caused this thumping noise in the rear of a vehicle when braking. After tearing apart the rear of the vehicle, lubing every bushing, and checking the clearances of every part imaginable, I came to the conclusion that it’s the rear drums that cause the noise.
Many cars have drum brakes in back, where a shoe stops the car by pressing on the inside of a metal drum. Brake drums, like rotors, get resurfaced once in a while. The cutting bit on the brake lathe removes the old braking surface and leaves a nice new mating surface. During this procedure, the cutting bit will create a groove in the brake drum so slight that the naked eye can’t see it; it’s like a groove on a vinyl record that the needle of the record player follows.
When the brake shoes ride on the new surface, they will follow the groove like the needle of your record player follows a track. If the groove is interrupted, the shoes snap back, hitting the backing plate. This phenomenon happens very quickly, causing a thumping noise that will drive you crazy and wondering if your car is falling apart or even safe to drive.
There are several ways to fix this noise. One is to replace the rear drums. A second way, less drastic, is to remove the drums, install them on a lathe, and sand the crap out of the mating surface with coarse sandpaper. The third way I found by trial and error and pure frustration is a quick fix using the emergency brake.
You will not find this procedure in any service manual or car repair manual, not even on car repair talk radio. It can be dangerous if not performed correctly so please be careful. Nevertheless, I have done it on over 100 cars, including family members’ cars, and I would not recommend it if I thought it damaged the vehicle.
How this works is that you get your rear brakes to do 100% of the braking for a few seconds at a time, instead of their usual 30%, and this will cause the brake shoes to polish the grooves out of the drum. For safety reasons, only try this on cars that have an emergency brake handle in the center console; emergency brakes that come up out of the floor can’t be set and released quickly enough.
Drive your car in a remote area with little or no traffic at a speed of about 40 miles an hour. Lightly pull up on the emergency brake handle while holding the release button; this is so the emergency brake handle won’t lock in the braking position, and you can release it quickly. Only hold the emergency brake on for about three seconds because you don’t want to overheat the drums. Do this three to five times, while keeping a steady speed; the noise should disappear, or at least be 90% gone. Then drive the car at normal speeds and use the brakes the way you normally would.
If the noise has not changed, you may have a different thumping noise than what I have described here in this article. Give up on this remedy and try something else.
My sister came to me with this noise after she had her brakes checked at her local garage. They had adjusted her rear brakes so the emergency brake handle had less free play in it, and this is when her troubles began. I took her car out on a test drive for about 10 minutes, performed the procedure described here, and poof, the noise was gone. She was happy because the garage that had caused the noise had no idea how to fix it.

3. "My Brakes Squeak"

A brake squeak can be very annoying, and furthermore might mean something. It may be a sign of danger of some kind, or it may just be a sign of cheap brake pads.
The most common brake squeak is caused by inferior pads. A cheap brake job sounds good when you’re paying for it, but it may come with years of painfully annoying brake squeaks. Cheap brake pads have large metal flakes in the brake material, and when you press the brakes lightly and a flake drags along the rotor, it will squeak. The squeak may go away when that particular flake wears away, but usually there is another metal flake right behind it. The best way to avoid this type of noise is to choose quality brake pads.
If your brakes are squeaking or squealing while driving down the road, but the noise goes away when you press on the brakes, I have a hunch that your brake wear indicator is hitting the rotor and causing the noise. The wear indicator is a small metal tab fastened to the brake pad. When the brake pads are worn down and need replacing, this metal tab starts to drag along the rotor, warning the driver of the potential problem. Don’t ignore the noise too long; the brake pads are thin and need servicing very soon, for safety and to protect the other parts of the braking system.



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