Master Cylinder

Master cylinders are used on braking systems to turn the mechanical power that is provided when you step on the brake pedal into the hydraulic power that is needed to apply the brakes and slow or stop the vehicle.

This works in conjunction with the brake vacuum booster. The brake master cylinder is where the brake fluid reservoir is located on most vehicles. The reservoir stores the fluid until it is needed.

The master cylinder has two pistons that direct hydraulic pressure to the front an rear brakes. If the fluid gets low because of a leak, air enters the system and you will have a condition of a spongy brake pedal or a pedal that fades to the floor when holding steady.