Your car's master cylinder provides the car's braking system with enough pressure for its hydraulic functions when you apply the brake pedal. A working master cylinder plays an integral role in your car's ability to stop.
Applying the Brakes
When the master cylinder is resting, heated brake fluid expands away from the calipers and brake lines and moves up to the master cylinder brake fluid reservoir. When you apply the brake pedal, the pedal linkage and master cylinder parts prevent the fluid from entering the reservoir and force it to remain in the brake lines as it heats up and expands to provide stoppage.
Releasing the Brakes
Releasing the brake pedal allows all the expanded fluid to pass through the master cylinder and enter the reservoir. This release in turn releases the pressure from the brake lines and the braking components located on the wheels, allowing your car to continue to accelerate ahead or in reverse.
Master Cylinder Troubles
If the master cylinder's ports ever become plugged, the fluid may maintain a certain temperature that could cause the brakes to self-apply at any given moment while driving. These ports are the main area of the master cylinder that require inspection.
