The wheel cylinder is a hydraulic actuator that uses brake fluid to push the brake shoes against the brake drum. If the wheel cylinder fails, brake fluid can leak from the back of the drum.
Brake line leak
Even though you may not see any visible brake line leaks, it is still possible for brake fluid to leak from a damaged or corroded brake line. Brake lines are typically made of steel or copper, and they can rust or corrode over time. If a brake line is damaged, it can leak brake fluid.
Defective brake proportioning valve
The brake proportioning valve is a device that regulates the amount of brake fluid that is sent to the rear brakes. If the brake proportioning valve is defective, it can cause brake fluid to leak from the back of the drum.
Master cylinder failure
The master cylinder is a hydraulic pump that generates the pressure that forces brake fluid through the brake lines. If the master cylinder fails, brake fluid can leak from the back of the drum.
Rear axle seal failure
The rear axle seal is a rubber seal that prevents brake fluid from leaking from the rear axle housing. If the rear axle seal fails, brake fluid can leak from the back of the drum.
