Rick's Free Auto Repair Advice

Brakes makes noise

Brake noise is a common complaint. The brake noise can mean the brake pads or brake rotors are worn, or they can simply mean the brake pads, hardware, or slide pins require cleaning and lubrication. Let’s look at the most common brake noise and their most likely causes.

This article is one in a series. If you’d like more information on brakes, click on the following links:

How much should a brake job cost?

What’s the difference between economy and premium rotors?

Why do brakes pulsate? How to prevent pulsation?

What brake pads should you buy? Ceramic or semi-metallic?

 

Brakes squeal

Brakes pads and shoes rub against a spinning rotor or drum. Over time, the rotors and drums develop grooves and the brake pads and shoes act like a phonograph stylus. So the brake pads and shoes literally play the rotor or drum as if it’s an old fashioned vinyl record. Car makers build in sound isolation techniques to reduce or eliminate this type of annoying noise transmission. They use noise reduction shims, abutment hardware, and specially designed high temperature synthetic brake grease.

Brake pad noise reduction shim

Brake pad noise reduction shim

If the noise reduction shim deteriorate they’ll transmit more noise. The shims are supposed to be replaced during a brake job. But some shops and most DIYers try to cut corners and reuse old shims. That’s a really bad idea. The same thing applies to abutment hardware. These stainless steel clips are designed to maintain just enough pressure on the brake pad backing plate to prevent vibration while allowing the pad to slide so it can apply and release. As the abutment hardware is heated by brake application and ages, it loses spring tension. That allows the brake pad backing plate to vibrate. In addition, abutment hardware can rust and prevent the brake pad from retracting, causing it to remain in contact with the rotor for prolonged periods. Both conditions cause the brakes to squeal.

 

abutment hardware, brake hardware, pad slide

Abutment hardware – new versus old and rusted

To correct the situation, replace the noise reduction shims and abutment hardware. Clean the abutment areas shown in these photos. Then apply a light coating of high temperature synthetic brake grease to the brake pad backing plate ears and abutment hardware. The brake grease lubricates and cushions the vibration.

 

On drum brakes, make sure there’s adequate friction material remaining on the shoe web. Then clean and lubricate the three pivot points for each shoe. Make sure the automatic adjuster is free of rust and turns freely. Install new retraction and hold-down springs. Then adjust the shoes.

 

Grinding Sounds

caliper pin

Corroded caliper slide pin can cause caliper to bind

Grinding noise are commonly caused by a binding condition. Floating style brake calipers are the most common style, and they must move freely on the caliper slide pins. Even a small amount of slide pin corrosion can prevent the caliper from releasing properly. That keeps pressure on the brake pads, causing them to overheat and create a grinding sound.

 

To diagnose a grinding condition, compress the caliper piston

caliper slide bolt, caliper pins, slide pin, caliper hardware

New caliper pins

slightly, remove the caliper and check the slide pins for ease of movement. If they don’t slide freely, try applying a high temperature synthetic brake grease. If they still don’t slide freely, replace the pins or bracket. Depending on the condition of the brake pads, you may need to replace them. And, if the rotor is heavily scored, replace it. To break rotor glaze, some shops use a random orbital sander with 120-grit sandpaper to apply a non-directional finish to the rotor. If you have a random orbital sander, you can try this approach. If that’s not enough to return the rotor to a non-grinding condition, replace the pads and rotors as a set.

©, 2013 Rick Muscoplat

Posted on by Rick Muscoplat

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