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9.3 BRAKE SERVICE; AUTOMOBILE REPAIR AND MAINTENANCE

By Don Patten

Don Patten is a leading expert in automotive education. His text book Automotive Service Basics published by Prentice Hall is used in automotive instruction courses world wide.

We want our brake system to be very dependable. Most of us do not give the brake system much thought until the vehicle does not stop right, or we hear noises when the brakes are applied. There are two brake systems, the regular service brakes and the parking brake system. A large percentage of the braking is accomplished by the two front wheels. This is because the vehicle weight is transferred to the front as the vehicle stops. You would expect the front brakes to wear faster than the rear. The parking brake is used to keep the vehicle in place after it is stopped. Most people never use the parking brake and depend on the transmission to keep a vehicle from rolling after it is parked. This can result in transmission damage if the vehicle is hit by another vehicle. The vehicle can then roll if it is parked on an incline. A friend of mine did not set his parking brake when he parked in his very steep driveway. The vehicle started to roll and went out the drive, glanced into his neighbor's house, and ended up in a pond at the back.

State inspections include both sets of brakes. It is the responsibility of the vehicle owner to keep his brakes in good condition. Faulty brakes can make the owner liable if an accident occurs.

== Master Cylinder Service

The master cylinder should be checked for correct fluid level each time the oil level is checked. The correct level is 1/4" from the top of the reservoir. When the fluid is low, use DOT three or four brake fluids made for disc brake systems. This fluid can withstand the heat developed by the disc brake systems. At the time you check the level, check the fluid condition. Dirty brake fluid would require a system flush and change.

== Leaks

Check on the inside of all four wheels for brake fluid leaks. There will be black streaks on the inside of the tires if the wheel cylinders or calipers are leaking. Trace all the lines and inspect around the master cylinder for leaks. Sometimes if the master cylinder is damaged, it will allow brake fluid to leak inside the vehicle onto the floor mat. Place some of the fluid on your finger and smell it. If it smells like brake fluid, replace or rebuild the master cylinder. A constantly low master cylinder reservoir indicates a leak somewhere in the system. This is serious and the cause should be found immediately.

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== Pedal Feel

A spongy pedal means air has entered the system. The system has to be bled (air removed) to be safe. A low pedal, brake light "ON," and longer stopping distance means either the front or rear brake system has failed. A vibration on the pedal as the brakes are applied means either the drums or the rotors are warped. Any pedal feel different from what you have come to expect should be checked out.

== Noise

A scratching noise when the brakes are applied coming from the front of the vehicle indicates worn out disc brake pads. Repair these immediately as the scratching noise is a warning built into the system to prevent damage to the rotors. A grinding noise in the rear of the vehicle as the brakes are applied is an indication of worn out brake shoes.

== Parking Brake

Apply the parking brake. The vehicle should not roll. If the vehicle can not be held in place by the parking brake, it should be adjusted.

== Lights

When the service brakes fail or the parking brake is applied there will be a red indicator light on the dash to warn the operator. If the light will not go out when the parking brake is applied there is a system failure. When the service brakes are applied there should be red lights in the rear that come on to warn the other drivers you are applying the brakes to stop. Make sure these lights are working.

== State Vehicle Inspection

Brake lights, leaks, parking brake, and general brake condition will be checked during an inspection. It is the responsibility of the owner to keep the brakes working properly in between inspections. If faulty brakes cause an accident, the owner is at fault.

Pedal feel, warning lights, sounds, and visual inspections all make up brake service. Learn to do these simple checks.

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