Automobile brake noise by itself is seldom a serious problem; however, it can sometimes indicate that a much more serious issue is developing. It is also one of the most irritating and embarrassing problems from the perspective of the driver and passengers. Drum brakes, which are used on the rear wheels of many cars, can make a different range of noises than disc brakes, and learning how to address these noises can make for more peaceful motoring while avoiding more serious problems down the road.
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Things you need
- Lug nut wrench
- Car jack
- Jack stands
- Brake micrometer or large Vernier caliper (capable of measuring at least 10-12 inches)
- Shop rags
- Wire brush
- Brake cleaning spray
- Dripping pan
- High-temperature brake grease
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. Determine the type of noise, such as squealing, grinding or thumping. Think about any other symptoms that accompany the noise, such as vibration, reduced braking performance or brake grabbing. Make a list of everything you know about the problem to help in the diagnosis.
Wait for the new shoes to wear in. It will take about 300 to 400 miles of city driving before the new shoes wear in with the drum, so 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 shoe linings. Some shoes are made with hard lining material, and brake squeal is normal when this is used. In this case, a change to a softer lining material may make the noise go away.
Inspect the brake linings to see if they are worn out or damaged. If the lining is completely worn or has failed, then the metal backing on the shoe will contact the drum during braking, and a loud grinding or scraping noise will result.
Check that the drum is not out-of-round and that all brake parts are secured in their proper positions. If the drum is not round, then the brakes will vibrate, and a rapid throbbing sound will be heard. If the sound is more like a sharp, rapid chattering, then something in the brake assembly is likely loose. Inspect the brakes immediately.
Examine the parking brake. If there is a continuous faint squeaking or squealing 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 both the handle or pedal end in the passenger compartment and at the brake end and look for signs of rust or corrosion.
Loosen the lug nuts on both rear wheels with a lug nut wrench. Raise the rear of the automobile with a jack and support it on axle stands at the designated support points. Remove the rear wheels. It is possible to work on one wheel at a time, but it is useful to compare the brake assemblies of two wheels, especially if one side is making noise but not the other.
Remove the nuts that hold the brake drum to the hub and pull the drum straight off the hub assembly. If corrosion and rust have seized the drum onto the hub assembly, it can be loosened by firmly tapping the drum on the outside shoulder with a hammer or mallet. Do not hit the drum on the inside edge where the drum meets the backing plate and do not pry the drum against the backing plate. With the drum removed, the brake assembly is now visible.
Inspect the brake components carefully. Start with the drum. Check the inside surface for scoring, deep grooves and other signs of abnormal wear. Look for excessive rust, corrosion or discolouration of the metal. If the inside of the drum shows any abnormal signs, then the drum should be machined. If there are any cracks or spots that are glazed or deeply pitted, then the drum should be replaced. Measure the inside drum diameter in several locations using the brake micrometer. All diameter measurements should be the same. If they are not, then the drum is out-of-round and should be machined. Compare the measured drum diameter to the manufacturer's specifications; and if the measured diameter exceeds the specified maximum diameter, the drum is worn out and should be replaced.
Check the brake shoes. Look for any foreign material embedded in the surface of the lining. Inspect for damage or scoring of the lining material. Measure the thickness of the shoe linings; if they are thinner than the manufacturer's recommendations, then they should be replaced. Check the steel shoe for signs of damage or bending. Damaged shoes should be replaced.
Inspect the backing plate. Check for excess corrosion, especially at the points where the shoes touch the backing plate. Look for any sign that the backing plate may be bent or distorted.
Check all brake components to ensure they are securely and properly fastened and that they are clean and free from excessive corrosion. Check the brake on one side of the car against the brake on the other side. Look for any heavy build-up of dust and dirt anywhere in the brake assembly since this is the major cause of drum brake noise. Be sure the springs are in good shape and properly fastened at both ends. Verify that the clips or pins that hold the brake shoes are in good shape and properly fastened at both ends. Look for heavy dirt build-up or corrosion on the adjuster star wheel.
Clean the entire brake assembly with brake cleaning fluid spray. Spray all parts liberally and wipe away any dirt and corrosion with a rag. Place a dripping pan under the brake assembly to catch the used fluid and dispose of it in accordance with local regulations. Use a rag or small wire brush to loosen stubborn dirt and corrosion. Clean the inside of the drum in the same manner.
Lubricate the various contact points with high-temperature brake grease. Lubricate the points where the brake shoes contact the backing plate. Apply grease to the shoe hold-down pins and the adjuster lever pivot point. Lubricate the threads on the adjuster star wheel. Take care not to get any grease on the lining surfaces of the brake shoes or on the inside of the drum.
Reinstall the drums. Remount the wheels and lower the vehicle. Test the brakes.
Tips and warnings
- Take care not to breathe in brake dust. This dust can contain asbestos and metals that are health hazards. Do not remove dust by blowing. Also, take care not to breathe in fumes from the brake cleaning fluid. Work in a well-ventilated area.
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