|JIM’S CORNER – AUTO REPAIR HELP|
PARKING BRAKE (EMERGENCY BRAKE)
The emergency or parking brake is used as a mechanical means to apply the rear brakes for parking or in the event of failure of the brake hydraulic system. Application of the emergency brake is accomplished through a hand or foot operated lever. The operating lever contains a ratchet assembly that allows the brake to be locked in place. A brake warning light switch is connected to the parking brake lever assembly and is used to illuminate the brake lamp when the emergency brake is applied. Diagnosing problems involving the parking brake are fairly straightforward. Refer to your auto repair book for the design details pertaining to your particular vehicle’s parking brake configuration, though most designs are very similar if not identical.
The emergency brake is applied by a cable attached to the emergency brake lever. The cable is used to actuate parking brake components located in the rear brake system. Typical drum brake designs use a lever to move the brake linings against the brake drum surface, to apply the parking brake. When the emergency brake cable is moved to the apply position, the lever will force the brake shoe that it is attached to, into the surface of the brake drum. At the same time, the lever will also force the opposite shoe into the brake drum by means of a link placed between the brake shoe and the lever.
Rear disc brake systems typically use one of two different systems as an emergency brake. The most common design uses a lever to actuate an internal screw assembly, at the rear caliper. The screw assembly rotates to apply pressure to the caliper piston, which in turn clamps the brake pads against the brake rotor. A second design incorporates an internal brake drum on the inside of the rear disc brake rotor. Shoes are attached to a small backing plate and are actuated by cable only. When the emergency brake is applied, the shoes are forced against the braking surface on the inside the brake rotor, causing the automobile to slow or even stop. I cannot stress how important it is to make sure the emergency brake is operating flawlessly; it can save your life. If any problems, take your vehicle to an auto repair shop or dealership and have it inspected.
(Jim is a lifelong fan of Dodger Baseball and used to race sprint cars in the 1980s.)