Automobile & Light Truck Certification Test A5 BrakesDrum Brake Diagnosis and RepairMedium
During a drum brake service, a technician notes that the brake shoes are contaminated with axle grease. Which of the following is the most likely source of this contamination?
- AA leaking rear axle seal
- BA ruptured wheel cylinder boot
- CA leaking master cylinder
- DOver-lubrication of the parking brake cable
Show answer & explanationAnswer & explanation
Correct answer: A. A leaking rear axle seal
Axle grease contamination on drum brake shoes typically originates from a leaking rear axle seal. This seal prevents differential or axle lubricant from escaping the axle housing and reaching the brake components.
Why the other options are wrong
- B. A ruptured wheel cylinder boot would leak brake fluid from the wheel cylinder, not axle grease.
- C. A leaking master cylinder would leak brake fluid, not axle grease, and typically affects all brakes.
- D. Over-lubrication of the parking brake cable might cause stickiness, but not grease contamination on the shoes.
Axle Seal Leak
A leaking axle seal allows differential or axle lubricant to escape the axle housing, often contaminating nearby brake components like drum brake shoes.
- Causes grease contamination on drum brake shoes.
- Leads to reduced braking effectiveness and potential pulling.
- Requires replacement of the axle seal and contaminated brake parts.
Memory trick: Axle Leaks Grease, Brakes Lose Peace