Some vehicles still have drum brakes or a combination of discs and drums. Passenger cars with this combination will have the drum brakes on the rear. Brake linings should be checked approximately every 15,000 kilometers (10,000 miles). The objective of this procedure is to show you how to check wheel cylinders, drum brake linings and measure brake drums.
Part 1. Preparation and safety
- Check wheel cylinders, drum brake linings and measure brake drums.
Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:
- Work clothing - such as coveralls and steel-capped footwear
- Eye protection - such as safety glasses and face masks
- Ear protection - such as earmuffs and earplugs
- Hand protection - such as rubber gloves and barrier cream
- Respiratory equipment - such as face masks and valved respirators
If you are not certain what is appropriate or required, ask your supervisor.
- Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.
Points to note
- Brake linings should be checked approximately every 15,000 kilometers (10,000 miles).
- Check under the dust cap to make sure that the wheel cylinder is not leaking. If you find a leaking wheel cylinder, report it to your supervisor.
Part 2: Step-by-step instruction
- Remove the drums
Some vehicles still have drum brakes or a combination of discs and drums. Passenger cars with this combination will have the drum brakes on the rear. Remove the brake drums. Be careful when you touch the brakes, they may be hot if the vehicle has been driven recently.
- Check wheel cylinders and linings
Inspect the external portion of the wheel cylinder. If the backing plate is covered with an oily substance you will need to determine if it is brake fluid or grease. Brake fluid will wash away with water so try washing it off. If it does not wash off then it is probably grease from a faulty seal. Carefully lever the rubber dust seals back, and inspect the inner portion of the cylinder for any signs of leakage.
- Check the brake shoes
Check the thickness of the brake shoe lining. You will need to consult the shop manual for the allowable minimum thickness. If the thickness is at this point or close to the minimum you must inform your supervisor. Also, if the brake shoe linings are covered in oil or grease they must be replaced. Report any signs of contamination or leakage to your supervisor.
- Check and measure the drum
Visually inspect the drum-braking surface for scoring. Any large score marks mean that the drum will have to be machined or replaced. Measure the inner diameter of the brake drum at several points around the circumference. Consult the shop manual for the specifications for an out-of-round condition. If the reading is outside the manufacturer’s specification, report it to your supervisor.
- Reassemble the drum brake
Reassemble the drum brake. Repeat the procedure for the other drum brake assemblies .