PROPER CARE
Inspecting Your Drum Brakes
*HARD*
You should inspect your drum brakes, if so equipped, every six months or 5,000 miles. It is advantageous to coincide the drum brake inspection with the tire rotation since the tires have to removed to inspect the brakes. They may as well be rotated after the brake inspection. Use the following procedure to examine your drum brakes:
- Park the vehicle on level ground with the engine OFF, the parking brake engaged, and the transmission in PARK (for automatic) or REVERSE (for manual). Allow the brakes to cool if your car has been driven recently, since the temperature of brake linings may reach as high as 500° F.
- Loosen the lug nuts on both rear wheels with a tire iron. Elevate the vehicle rear end on safety stands and block the front wheels. Clean any dirt or rust from the lug bolts (studs). Remove the lug nuts from the studs and both rear wheels from the vehicle.
- Loosen the adjustment nut on the parking brake cable equalizer. The nut will be in the center of a U-shaped bracket underneath the car. This will relieve all tension in the parking brake system. See Adjusting Your Parking Brake.
- Rotate the brake drums by hand. If contact is heard between the brake lining and its brake drum, the brake shoes need to be retracted through adjustment of the star wheel. In this case, consult your owner's manual for the exact procedure. However, the star wheel is usually accessed through a small slot in the backing plate. The slot may be covered with a rubber plug; if so, remove it. Use a small screwdriver to disengage the brake adjusting lever from the star wheel teeth.
- Next, while maintaining the adjusting lever in a disengaged position, insert a brake adjusting tool or second screwdriver into the same access slot. Repeatedly move the handle in an upward direction to rotate the star wheel and retract the brake shoes. It may take about four or five turns. Do not damage the star wheel teeth or the automatic self-adjuster may not function.
- Remove any metal clips or speed nuts that may be securing the brake drum to the axle. Remove brake drums from the rear axle by pulling them off the axle shaft flanges. If the drums still cannot be removed after the brake shoes have been retracted, they may be corroded onto the axle shaft flange. In this case, reverse the star wheel adjustment to expand the brake shoes back to their original position. Have a professional automotive technician service the brakes instead.
- Visually inspect the brake linings on the
primary shoes and
secondary shoes of both
wheels.
Be sure the brake linings have sufficient thickness. They should be a minimum of 1/16" thick, or about as thick as a nickel, if they are glued to the brake shoe. If the linings are riveted to the shoe, their surfaces should be at least 1/16" above the rivet heads. If the linings are too thin, have them replaced. Linings must be replaced in sets of four, that is, primary and secondary shoes for both left and right wheels. Do not replace linings individually.
- Observe these conditions if they exist:
- Linings should wear equally on both wheels. If one wheel's brake linings have worn more than the others, the former wheel may have a rough drum. The drum should be machined or replaced.
- Linings should wear equally from side-to-side. If not, the drum may be tapered and should be replaced.
- Linings should wear equally from end-to-end. If not, the drum may be out of round and should be replaced.
- Replace the linings if they are contaminated with dirt, brake fluid, axle grease, or differential oil. Also correct the source of the contamination problem.
- During your inspection, do not touch the brake linings with an oily rag or greasy fingers. Dirt will adhere to the surface and cause extra brake wear.
- Inspect the brake shoes for cracks and distortions. If the shoes are faulty, they must be replaced. Inspect the springs as well. If the springs are damaged or stretched, have them replaced.
- Visually inspect the interior surface of the brake drum for abnormal wear.
Look for gouges (scoring), cracks, burns, and other defects. Drum surfaces
should be smooth.
If drum defects are superficial, they can be removed by machining ("turning") the drum. This process removes metal from the drum's interior surface by use of a lathe. However, the inside surface of the drum cannot be machined more than 0.060" deep, otherwise, the drum is substantially weakened and could crack in use. Drums must be replaced when defects are substantial. A professional automotive technician can help you decide whether to turn or replace a drum. - Inspect the wheel cylinders for fluid leaks. Gently pull back the rubber boots on each side of both wheel cylinders. If brake fluid is present, have the wheel cylinder repaired or replaced by a professional automotive technician. However, do not drive the car to the repair facility; instead, have it towed. Make sure all springs are firmly connected and not worn.
- After inspection, reverse the star wheel adjustment procedure previously performed. However, the star wheel may be directly accessed from the front this time. Engage the self-adjusting lever to the star wheel using a small screwdriver. The brake lining clearance with the brake drum will now adjust automatically when the car is stopped in reverse.
- Place each brake drum over the axle shaft flange. Make sure drums turn freely by hand. If not, adjust the star wheel from the slot in the backing plate. Hand tighten the lug nuts firmly but in an alternating fashion. Tighten the parking brake cable adjuster nut enough to remove most slack from the system.
- Lower the vehicle until the rear tire treads make ground contact. Finish tightening the lug nuts according to your manufacturer's specifications. Remove the safety stands and wheel blocks. Test the brakes in a deserted area.
- If your car has front-wheel drive, the above steps must still be followed for rear drum brakes. In addition, the inner and outer rear wheel bearings must be removed and replaced along with ancillary components. See Servicing Your Wheel Bearings.
The integrity of the brake system is important to the control of the vehicle and safety of its occupants. Repair or replacement of drum brake components requires special tools and skill and should therefore only be performed by a professional automotive technician.
