Automotive braking system

The braking system on all consumer vehicles consists of a simple hydraulic actuation. As your foot depresses the brake pedal force is applied to a master cylinder that displaces the ‘hydraulic oil’ in this case brake fluid. As this fluid is pushed from the master cylinder its force is transferred to the calipers or brake shoe actuator. This in turn pushes the brake pads or shoes against the rotor or brake drum creating friction which in turn slows/stops your vehicle.

Here are some basic terms and what they refer to

• Master Cylinder : This unit is the act as the reservoir and hydraulic pump for the braking system
• Brake Line: The steel or rubber lines that the brake fluid travels
• Brake Pad: A Metallic or ceramic like pad that creates friction on the brake rotor.
• Brake Shoe: A Metallic or ceramic like pad that creates friction on the brake drum.
• Brake Rotor: The circular device at the center of your wheel that acts as a medium for the brake pads to grasp.
• Brake Drum: The circular drum that fits over a pair of brake shoes. As the brake pedal is depressed the shoes are forced apart applying force against the inside of the drum to slow or stop the vehicle.
• Brake Caliper: The device that holds the brake pad in place and provides the squeezing force on the brake pads against the rotor.
• Brake fluid: The hydraulic fluid that transfers the power from your brake pedal to the brake shoe.
• DOT 3,4,5: Department Of Transportation, Type 3, 4 and 5 are specific to the chemical makeup of the product. Always use the manufacturer’s specified type, if not followed Brake failure can occur.

Why does brake fluid need to be checked and why does the level go down

1. The level goes down because the brake pads / shoes are worn.
   It is important that the brake fluid is checked periodically. When brake pads wear they cause the caliper pucks to move further out of the enclosure. This void gets filled with brake fluid from the brake reservoir. In the event the level drops below the low level there is danger of air getting into the closed hydraulic system.  If this happens the brake pedal will feel ‘spungy’ and braking performance will be diminished. The level is also a good indicator of brake pad/shoe wear.  
   
   Most newer style vehicles are equipped with a simple metal tab attached to the brake pad that scrapes on the brake rotor, this creates an annoying scraping or screeching sound while driving. This is a sign to get the brake replaced.
2. The level will go down if there is a leak. This is a catastrophic failure, contact a professional immediately and do not drive the vehicle.

A warped rotor

This can be detected when applying the brakes. Depending on the severity, a pulsing feeling will be detected when applying force on the brake pedal.
A warped rotor can be caused by the following.

1. A rotor can warp under heavy braking, usually from higher speeds or carrying a heavy load. The amount of heat that the brakes generate cause the rotor to expand, since this expansion is uneven across the rotor it will tend to warp. Granted this warping is not visible to the naked eye but can be detected with precision tools and can be felt in the brake pedal when depressed. The warping causes the brake pads to move in-and-out which is the pulsing you feel.
2. The second reason they are most likely to warp is from being warn. As the pads squeeze the rotor small amounts of material are worn off. The manufacturer accounts for this and builds the rotors thick enough to provide decent longevity. The manufacturer defines a minimum thickness tolerance which should be followed. The warping begins when enough material has been worn off and the rotor can no longer dissipate enough heat between braking application causing the rotors to warp. Worn rotors can usually be identified by a ‘lip’ around the outside of the rotor.
3. Generally the less expensive brake rotors tend to warp sooner then the more expensive ones. This is unfortunate. It will save you money in the long run if you purchase the more robust rotors. I highly recommend this especially if working on SUV type vehicles or frequent hauling or towing.

It is not possible for me to provide you with all the details on how to change the brakes on every car made. Granted they are all very similar but each manufacturer has their own way of designing them. I recommend purchasing a Chilton's manual for your vehicle, this easy to read manual will provide you with all the specifics to your make and model and outline all the technical knowledge to maintaining and or repairing your automobile.

To summarize, monitor your brake fluid periodically and listen for any peculiar noises. If you feel a pulsing feeling in the brake pedal or hear a constant annoying noise from the brake it is a good sign that your brakes need to be serviced.