How to Troubleshoot Auto Brake Systems

Drum brakes are becoming rare, but they are still used in some cars.

Modern brake systems have several main components: master cylinder, calipers, brake pads, rotors, wheel cylinders, brake drums and brake shoes. When these components fail, there are several symptoms that can be produced: vibration, grinding, squealing or leakage. No matter what the symptom, the brakes need to be checked to verify the problem so that it may be repaired. Not checking and repairing the problem can lead to catastrophic brake failure and may cause you to lose control of the vehicle.

Things You'll Need

• Floor jack
• Jack stands
• Ratchet
• Combination wrench set
• Socket set
• Hammer
• Penny

Instructions

Vibration

1. Loosen the lug nuts but do not remove them.

2. Jack up the vehicle and secure it with jack stands.

3. Put the vehicle in neutral.

4. Remove the lug nuts from the wheels.

5. Spin each rotor or drum with your hands. If they are harder to turn in certain areas, the rotors or drums are warped. Replace or resurface the rotors or drums.

Grinding

1. Use a ratchet and socket to loosen the lug nuts, but do not remove them.

2. Jack up the vehicle and secure it with jack stands.

3. Remove the lug nuts and the wheels.

4. Check the thickness of each brake pad by inserting the edge of a penny between the brake pad backing and the rotor. If the penny does not fit, the pads need to be replaced. On drum brakes, place the penny on the backing of the brake shoe and compare it to the thickness of the shoe. If the shoe is thinner, replace the shoes.

Squealing

1. Use a ratchet and socket to loosen, but not remove the lug nuts.

2. Jack up the vehicle and secure it with jack stands.

3. Remove the lug nuts and the wheels.

4. Check the thickness of each brake pad by inserting the edge of a penny between the brake pad backing and the rotor. If the penny does not fit, the pads need to be replaced.

5. Examine the brake rotor. The rotor should be dull. If it has a shine to it and the brake pads are of the proper thickness replace or resurface the rotors.

Leakage

1. Use a ratchet and socket to loosen, but not remove the lug nuts.

2. Jack up the vehicle and secure it with jack stands.

3. Remove the lug nuts and the wheels.

4. Examine the rear of the brake calipers. Look for any signs of dampness coming from the hose that bolts into the rear of the caliper. If leakage exists, remove the line, wrap the threads with thread tape and tighten the line with a wrench.

5. Remove the rear brake drum by pulling it off with your hands. You may need to tap the drum with a hammer to release it.

6. Examine the drum brakes and locate the wheel cylinder. The wheel cylinder is at the top and center of the brake assembly.

7. Pull the rubber boot off of each side of the cylinder and look for fluid. If fluid is present, replace the wheel cylinder and recheck.

8. Inspect all of the brake line connections, under the car and under the hood, for leaks. If any exist, disconnect the line, wrap the threads in Teflon tape, reconnect the lines and recheck.

9. Replace or rebuild the master cylinder if all other items have been replaced or are found to be operating properly.