Brake System  The modern automotive brake system has been refined for over 100 years and has become extremely dependable and efficient. The typical brake system consists of [url=http://abbysenior.com/mechanics/brakes.htm#Disc Brake]disk brakes[/url] in front and either disk or [url=http://abbysenior.com/mechanics/brakes.htm#Drum Brake]drum brakes[/url] in the rear connected by a system of [url=http://abbysenior.com/mechanics/brakes.htm#Brake Lines]tubes and hoses[/url] that link the brake at each wheel to the [url=http://abbysenior.com/mechanics/brakes.htm#Master Cylinder]master cylinder.[/url] Other systems that are connected with the brake system include the [url=http://abbysenior.com/mechanics/brakes.htm#Parking Brakes]parking brakes[/url], [url=http://abbysenior.com/mechanics/brakes.htm#Power Brakes]power brake[/url] booster and the [url=http://abbysenior.com/mechanics/brakes.htm#Anti-Lock Brakes]anti-lock[/url] system.  When you step on the brake pedal, you are actually pushing against a plunger in the master cylinder which forces hydraulic oil ([url=http://abbysenior.com/mechanics/brakes.htm#Brake Fluid]brake fluid[/url]) through a series of tubes and hoses to the braking unit at each wheel. Since hydraulic fluid (or any fluid for that matter) cannot be compressed, pushing fluid through a pipe is just like pushing a steel bar through a pipe. Unlike a steel bar, however, fluid can be directed through many twists and turns on its way to its destination, arriving with the exact same motion and pressure that it started with. It is very important that the fluid is pure liquid and that there is no air bubbles in it. Air can compress, which causes a sponginess to the pedal and severely reduced braking efficiency. If air is suspected, then the system must be bled to remove the air. There are "bleeder screws" at each wheel cylinder and caliper for this purpose. On a [url=http://abbysenior.com/mechanics/brakes.htm#Disc Brake]disk brake[/url], 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 disk (rotor) which is attached to the wheel, forcing it to slow down or stop. This process is similar to a bicycle brake where two rubber pads rub against the wheel rim creating friction. |
 With [url=http://abbysenior.com/mechanics/brakes.htm#Drum Brake]drum brakes[/url], 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, causing the wheel to stop. In either case, the friction surfaces of the [url=http://abbysenior.com/mechanics/brakes.htm#Brake Pads]pads[/url] on a disk brake system, or the shoes on a drum brake 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. |
| Let's take a closer look at each of the components in a brake system and see where other problems can occur... Master Cylinder  The master cylinder is located in the engine compartment on the firewall, directly in front of the driver's seat. A typical master cylinder is actually two completely separate master cylinders in one housing, each handling two wheels. This way if one side fails, you will still be able to stop the car. The brake warning light on the dash will light if either side fails, alerting you to the problem. 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 your foot applies steady pressure. Letting go of the pedal and immediately stepping on it again brings the pedal back to normal height. |
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