The Automotive Brake System
The typical brake system consists of disk brakes in the front and either disk or drum brakes in the rear. As the illustration below depicts, the brakes are connected by a system of tubes and hoses that link the brake at each wheel to the master cylinder. Other components which are connected with the brake system include the parking brakes, power brake booster, and the anti-lock system.
When you step on the brake pedal you are actually pushing against a plunger in the master cylinder which forces brake fluid through a series of tubes and hoses to the braking unit at each wheel.
On a disk brake system the fluid from the master cylinder is forced into a caliper where it presses against a piston. The piston, in-turn, squeezes two brake pads against the rotor, which is attached to the wheel, forcing it to slow down or stop. The disk brake system is the best braking system available for most vehicles and transportation sources. Disk brakes are used to stop everything from cars and trucks, to locomotives and jumbo jets. Disk brakes wear longer, are less affected by water, are self adjusting, self cleaning, less prone to grabbing or pulling, and stop better than any other system around.
If the brake system has drum brakes, fluid is forced into the wheel cylinder, which pushes the brake shoes out so that the friction linings are pressed against the drum, which is attached to the wheel, forcing it to slow down or stop.
In either case, the friction surfaces of the brake pads or shoes convert the forward motion of the vehicle into heat. Heat is what causes the friction surfaces (linings) of the pads and shoes to eventually wear out and require replacement. Additionally, damaged or worn parts on the brake caliper or brake drum assembly can cause premature or excessive wear on the brake pads or linings.
The master cylinder is located in the engine compartment; directly in front of the driver’s seat on the firewall. A typical master cylinder is actually two completely separate master cylinders contained in one housing — each handling two wheels. Essentially this is a built-in safety feature to ensure that should one cylinder fail, the other cylinder will continue to function so you will still be able to stop the vehicle.
Master cylinders have become very reliable and rarely malfunction; however, the most common problem that they experience is an internal leak. This will cause the brake pedal to slowly sink to the floor when you apply steady pressure with your foot. However, letting go of the pedal and immediately stepping on it again brings the pedal back to normal height.
If your brake pedal is experiencing this type of behavior you should promptly schedule your vehicle to have your brake system inspected and serviced.