ASE G1 Auto Maintenance and Light RepairBrakesMedium
A technician is performing a brake inspection on a rear drum brake system. They notice that one of the brake shoes is heavily contaminated with brake fluid. Which component is MOST likely leaking?
- AThe brake hose
- BThe wheel cylinder
- CThe master cylinder
- DThe parking brake cable
Show answer & explanationAnswer & explanation
Correct answer: B. The wheel cylinder
In a drum brake system, the wheel cylinder is located inside the drum and is responsible for pushing the brake shoes outward when hydraulic pressure is applied. A leak from the wheel cylinder would directly contaminate the brake shoes with fluid.
Why the other options are wrong
- A. A leaking brake hose near the wheel would cause fluid to spray externally or drip, but it's less likely to directly saturate the inside of the drum brake shoe unless catastrophically failed.
- C. A leaking master cylinder would typically cause fluid loss from its reservoir or leak into the brake booster, not directly onto the rear brake shoes.
- D. The parking brake cable is a mechanical component and does not contain brake fluid, so it cannot be the source of a fluid leak.
Wheel Cylinder Leak
A common failure point in drum brake systems where hydraulic fluid leaks past the internal seals of the wheel cylinder, contaminating brake shoes.
- Causes reduced braking effectiveness and pull to one side.
- Contaminated shoes must be replaced, along with the leaking wheel cylinder.
- Fluid appears on the inside of the drum brake assembly.
Memory trick: The wheel cylinder weeps inside the drum, soaking the shoes.