Automobile & Light Truck Certification Test A5 BrakesDrum Brake Diagnosis and RepairMedium
A technician is performing a pre-inspection of a drum brake system. They notice that the brake drum has an excessive amount of rust and corrosion on its inner friction surface, making it rough. What is the most appropriate action to take?
- AApply anti-seize compound to the rusted areas.
- BResurface the drum if within machining limits.
- CClean the drum with brake cleaner and reinstall.
- DReplace the brake shoes only.
Show answer & explanationAnswer & explanation
Correct answer: B. Resurface the drum if within machining limits.
Excessive rust and corrosion on the friction surface of a brake drum will reduce braking effectiveness and cause noise. If the drum is still within its maximum diameter machining limits, resurfacing (turning) it will restore a smooth, clean friction surface. If beyond limits, it must be replaced.
Why the other options are wrong
- A. Anti-seize is not for friction surfaces and would contaminate the brakes.
- C. Cleaning alone will not remove deep rust or restore a smooth surface.
- D. Replacing shoes without addressing the drum will lead to rapid wear of the new shoes and poor braking.
Brake Drum Surface Rust
Surface rust and corrosion on a brake drum's friction surface can cause noise, reduced braking effectiveness, and premature wear of brake shoes. It often requires resurfacing or replacement.
- Common on vehicles stored or driven in humid conditions.
- Causes grinding noise and reduced friction.
- Must be removed by machining or drum replacement.
Memory trick: Rust on Drum, Turn it Some (or Replace, if Done)