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 significant rust on the braking surface of the drum, but the drum shows no signs of scoring, cracking, or excessive wear. What is the MOST appropriate action?
- AReplace the brake drum immediately.
- BClean the rust off with a wire brush and reinstall.
- CMachine the brake drum to remove the rust.
- DLightly sand the rust off and advise the customer that it will likely wear off with normal use.
Show answer & explanationAnswer & explanation
Correct answer: D. Lightly sand the rust off and advise the customer that it will likely wear off with normal use.
Light surface rust on a brake drum that otherwise shows no damage is common, especially after a vehicle has been sitting. It will typically be worn off by the brake shoes during the first few brake applications. Machining or replacing the drum for only surface rust is unnecessary and costly.
Why the other options are wrong
- A. Replacing the drum is excessive for surface rust without other damage.
- B. While cleaning helps, light sanding and informing the customer is a more practical approach as the shoes will remove it.
- C. Machining is unnecessary and reduces drum thickness for only surface rust.
Brake Drum Surface Rust
Minor oxidation on the braking surface of a drum, typically occurring after periods of inactivity or exposure to moisture.
- Common and usually harmless
- Wears off with normal braking
- Does not require replacement or machining unless severe
Memory trick: Rust on the drum, just let it run.