The whole process of the braking system is powered by the release of the brake fluid which comes from the brake master cylinder. Nowadays, car manufacturers have separated their brake system into two circuits. The brake master cylinder is responsible for supplying the pressure to both circuits. The brake master cylinder is a part of the brake system that is attached to the brake booster. All the brake tubes and hoses going to the brakes in each wheel are attached to the master brake system. And using two pistons in the same cylinder it allows the driver to put pressure to the braking hydraulic system. When the pressure is applied on the brake pedal, the primary piston is pushed towards the linkages. As more pressure is applied on the pedal more pressure is also built in the cylinder and lines. These pressures between the primary and secondary piston forces the second piston to compress the fluid in its circuit releasing the fluid to the caliper. In turn, this fluid travels the hoses and tubes to move the pistons of the caliper which presses the brake pads against the rotors which clamps on the wheel to stop its rotation. Atop the brake master cylinder is a reservoir where the brake fluid is housed and which needs to be flushed annually to ensure that the Eagle Brake Master Cylinder last longer. Leak is one of the major problems of a brake master cylinder. It can leak in the rubber grommets, on the brake lines itself or at the back of the master cylinder. In case of leak, the pressure between the primary and secondary cylinders is lost thus the braking power will be affected. It is best that you have it checked when there is no resistance on the brake pedal because accidents can happen if any of your brake system components fail. For replacements, check out the wide selection we have in our online store.