Automotive Service Excellence (ASE) - Brake System

Terms in this set (40)

What are the major components of the brake system?
disc brakes
brake pads
calipers
rotors
drum brakes
drums
shoes
drum hardware
wheel cylinders
master cylinder
pressure differential valve
proportioning valve
brake fluid
brake hoses and lines
anti-lock brake system (ABS)
What are disc brakes?
brakes that use a pair of friction pads to squeeze against a flat disc or rotor when the brakes are applied
What are brake pads?
the friction linings used with disc brake systems
What are calipers?
parts that, in disc brake systems, are used to squeeze the brake pads against the rotors when brakes are applied
What is the purpose/function of calipers?
to squeeze the brake pads against the rotors when the brakes are applied
What are rotors?
discs that are either solid or vented and which cause the vehicle to stop based on the friction between them and the brake pads
What are drum brakes?
a type of brake system that uses a cylindrical drum as the friction surface for a pair of brake shoes
What are shoes?
the friction linings inside a brake drum
What is the purpose/function of shoes?
to squeeze outward against the inside of the drum to apply the brakes
What is drum hardware?
return springs
hold down springs
self-adjusters
cables, clips, or springs
What is the purpose/function of return springs?
to pull the shoes back away from the drum when the brakes are released
What are wheel cylinders?
the hydraulic component inside a drum brake that pushes the shoes out against the drum, it has two opposing pistons that move outward when pressure is applied
What is the purpose/function of wheel cylinders?
to push the shoes out against the drums
What is a master cylinder?
a component that applies hydraulic pressure to the calipers and wheel cylinders when the brakes are applied
What is the purpose/function of a master cylinder?
to push fluid through the brake lines to each wheel to apply the brakes (when the brake pedal is depressed)
What is a pressure differential valve?
a safety switch that turns on the brake warning light if there's a loss of pressure or fluid in either hydraulic circuit
What is the purpose/function of a proportioning valve?
to reduce hydraulic pressure to the rear brakes to maintain proper brake balance *some vehicles have a "load sensing" proportioning valve attached to the rear suspension to vary brake pressure according to vehicle load*
What is brake fluid?
a glycol-based hydraulic fluid used in brake systems
What is the purpose/function of brake fluid?
to apply the brakes
What are brake hoses and lines?
rubber hoses and steel lines that are found in the vehicle braking system
What is the purpose/function of brake hoses and lines?
to carry hydraulic pressure from the master cylinder to each brake
What is an anti-lock brake system(ABS)?
a system comprised of sensors that monitors wheel speed when braking
What is the purpose/function of an anti-lock brake system(ABS)?
to reduce the risk of wheel lockup and skidding on wet or slick surfaces
When should brake pads be replaced?
when their thickness reaches minimum specifications or a wear indicator makes noise; if the linings have become contaminated with grease, oil, or brake fluid; if the linings are unusually noisy
*front pads typically wear two to three times faster than the rear pads*
*the friction material in replacement pads should always be the same (or better) than the original pads*
*pads should always be replaced in pairs to maintain even braking*
When should calipers be replaced?
when there are fluid leaks due to worn piston seals, when there is sticking (which may be due to corrosion around the piston or corroded slides or bushings), when there is uneven pad wear (inner pad worn more than the outer pad), or if the calipers are damaged
When should rotors be replaced?
when they are worn to minimum service or discard specifications, when they are cracked, severely corroded, or have hard spots
When should drums be replaced?
when they've become worn, grooved, out-of-round, cracked, or worn beyond maximum inside diameter (ID) or discard specifications, or have hard spots
When should shoes be replaced?
when the lining thickness is worn to minimum specifications *the type of friction material on the replacement linings should be the same type (or better) than the original*
When should wheel cylinders be replaced?
when fluid leaks or when there is sticking
When should a master cylinder be replaced?
when fluid leaks past the piston or shaft seals, when the brake pedal slowly sinks to the floor when braking at a stop light, failure to hold fluid pressure
When should brake fluid be replaced?
when it has absorbed moisture and/or become contaminated over time
When should brake hoses and lines be replaced?
when corroded, leaking, cracked, or damaged *only used approved brake line tubing and never any other kind*
When should an anti-lock brake system (ABS) be replaced?
when there has been a failure of the system *sometimes, with "integral" ABS systems, which are attached to the master cylinder, the system may need to be replaced when the master cylinder is replaced or vice verse*
What different friction materials can be used on brake pads?
non-asbestos organic (NAO), ceramic, low-metallic, semi-metallic *on some applications, the inner and outer pads may use different friction materials*
When should return springs be replaced?
when they become weak (due to age) and allow the brakes to drag
When should self-adjusters be replaced?
when they are corroded and/or stick, causing increased pedal travel as the shoes wear
When should drum hardware generally be replaced?
in high mileage vehicles; when new shoes are installed
What is the difference between DOT 3 and DOT 4 brake fluid?
DOT 4 has a higher temperature rating *the type of brake fluid specified by the vehicle manufacturer should always be used*
What major components is an anti-lock braking system (ABS) comprised of?
wheel speed sensors
hydraulic modulator (including the ABS solenoid valves for each brake circuit)
ABS control module
pump
high-pressure accumulator
pump-relay
Compare/Contrast: Disc Brakes vs. Drum Brakes
disc brakes provide more stopping power, better cooling, and better fade resistance
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