CDL Air Brakes TestAir Brake System PartsHard
A driver is performing a pre-trip inspection and notices that the brake drums on the drive axles are discolored (dark blue or purple) and show signs of cracking. What does this indicate?
- AThe brakes have been severely overheated.
- BThe automatic slack adjusters are out of adjustment.
- CThe brake linings are too thick, causing excessive friction.
- DNormal wear and tear for high mileage vehicles.
Show answer & explanationAnswer & explanation
Correct answer: A. The brakes have been severely overheated.
Discolored brake drums (especially dark blue or purple) and cracking are classic signs of severe overheating. This overheating can lead to brake fade, reduced braking effectiveness, and potential structural failure of the drum, making it a critical safety defect.
Why the other options are wrong
- B. Misadjusted slack adjusters would typically cause a 'spongy' pedal or uneven braking, not direct discoloration or cracking of the drums from heat unless it led to continuous dragging.
- C. Thick linings would not cause this discoloration; overheating is the primary cause.
- D. While wear occurs, discoloration and cracking are not normal and indicate a serious problem.
Foundation Brakes Overheating
Excessive heat buildup in the brake drums and linings, often indicated by discoloration, cracking, or glazing, leading to reduced braking power.
- Caused by prolonged or heavy braking.
- Results in brake fade and damage.
- Discoloration (blue/purple) and cracking are key signs.
Memory trick: Blue Drums = Burnt Brakes.