AUT 101-Chapter 50 Review Question and Key Terms

Metallic linings-

brake friction material made from powdered metal that is formed into blocks by heat and pressure

Semimetallic lining-

brake friction materials made from a mixture of organic or synthetic fibers and certain metals; they do not contain asbestos

Synthetic lining-

brake friction materials made from nonorganic, nonmetallic, and nonasbestos materials; typically fiberglass and aramid fibers

Cup seal-a

circular rubber seal with a depressed center section surrounded by a raised sealing lip to form a cup

Static friction-

friction between two stationary objects or surfaces

10. The purpose of the master cylinder is to__________________.

generate the hydraulic pressure needed to apply the brake mechanisms

Caliper-

major component of a disc brake system. Houses the piston(s) and supports the brake pads

8. A three-function combination valve has a brake system failure switch, a______________ , and a ______________.

metering valve proportioning valve

Brake fade-

occurs when friction surfaces become hot enough to cause the coefficient of friction to drop to a point where the application of severe pedal pressure results in little actual braking

Nonasbestos organic linings (NAO)-

organic brake linings that are made of nonmetallic fibers bonded together to form a composite material

4. When the brakes are applied on a moving car, the frictional parts (brake ______ or ________ ) are forced against the rotating parts of the car (brake ______ or ______). The friction causes the rotating parts to slow down and stop. Just as the energy of the rotating parts is called kinetic _________, the friction used to stop them is called kinetic ___________.

pads or shoes rotors or drums energy friction

Aramid fibers-

refer to a family of synthetic materials that are stronger than steel but weigh little more than half of what an equal volume of fiberglass would weigh

Vent port-

the forward port in the master cylinder bore; it lets fluid pass between each pressure chamber and its fluid reservoir during operation

Rotor-

the rotating or freewheeling portion of a clutch; the belt slides on the rotor

5. Which of the following could cause an extremely hard brake pedal?

A leaking diaphragm in the vacuum power booster

7. Explain why a height-sensing proportioning valve is required on some vehicles.

Because the height-sensing proportioning valve provides two different brake balance modes to the rear brakes based on vehicle load

10. The hydraulic system of the hydro-boost and Power master is being discussed: Technician A says that the hydro-boost uses a power-steering pump. Technician B says that the Powermaster uses an electric motor-driven vane pump. Who is correct?

Both A and B

6. The basic frictional parts of a brake system are being discussed: Technician A says that the harder the frictional parts are pushed together, the higher the friction. Technician B says that the harder the frictional parts are pushed together, the more heat is developed. Who is correct?

Both A and B

1. Explain why bleeding air out of a hydraulic system is so important.

Fluids cannot be compressed, whereas gases are compressible. Any air in the hydraulic system is compress as the pressure increases. This action reduces the amount of force that can be transmitted by the fluid; therefore it is very important to keep all air out of the hydraulic system

2. Explain why modern hydraulic braking systems are dual designs, and why this is important.

If one circuit in the brake system fails, the other provides enough braking power to safety stop the car

11. Which of the following can lead to brake hose failure?

Improperly matched fittings

14. Which of the following is not a factor in determining the effectiveness of a brake system?

Lubricant

4. While discussing quick take-up master cylinders: Technician A says that this design allows for increased braking power. Technician B says that this design is only used on drum brake systems. Who is correct?

Neither A nor B

5. While bleeding a brake system: Technician A loosens the brake line fitting at the master cylinder to bleed the system if a bleeder screw is seized and cannot be loosened. Technician B uses shop air to push the fluid and air from the wheel units to the master cylinder. Who is correct?

Neither A nor B

9. Technician A says that the master cylinder should be bled before any individual wheel assembly. Technician B says that the bleeder screw should be closed before the brake pedal is released during manual bleeding of the system. Who is correct?

Neither A nor B

7. Vehicle dynamics during braking are being discussed: Technician A says that the rear of the car rises during braking. Technician B says that the front of the car lowers during braking. Who is correct?

Technician A and B

3. The metering valve portion of a combination valve fails: Technician A says that this means the entire combination valve must be replaced. Technician B says that metering part can be repaired. Who is correct?

Technician A only

1. A vehicle's power brakes are grabbing: Technician A says that the most likely cause is the power brake booster. Technician B says that a likely cause is greasy linings or scored drums. Who is correct?

Technician B only

2. While discussing what affects the amount of pressure exerted by the brakes: Technician A says that the shorter the line, the more pressure there will be. Technician B says that braking force will increase if the size of the pistons in master cylinders are increased. Who is correct?

Technician B only

8. Pressure bleeding is being discussed: Technician A says that metering and combination valves must be held open using a special tool during the bleeding operation to ensure good results. Technician B says that the pressure bleeder requires special adapters to connect it to the master cylinder reservoir. Who is correct?

Technician B only

5. What is the purpose of the master cylinder vent port?

The master cylinder vent port let fluid pass between each pressure chamber and its fluid reservoir during operation

6. What is the purpose of the master cylinder replenishing port?

The master cylinder vent port let fluid pass between each pressure chamber and its fluid reservoir during operation

3. Describe the functions of the hydraulic system combination valve.

Three-Function Valve performs the functions of the metering valve, brake warning light switch, and proportioning valve. One variation of two-function valves works the proportioning valve and brake warning light switch functions. The other performs the metering valve and brake warning light switch functions

12. True or False? Metering and proportioning valves balance the braking characteristics of disc and drum brakes.

True

9. Explain how vacuum is used to provide a power assist.

Vacuum generate application energy by opposing engine vacuum to atmospheric pressure. A piston and cylinder, flexible diaphragm, or bellows use this energy to provide braking assistance

Metering valve-

a component that momentarily delays the application of front disc brakes until the rear drum brakes begin to move. Helps to provide balanced braking

Quick take-up-

a dual master cylinder that supplies a large volume of fluid to the front disc brakes on initial brake application, which takes up the clearance of low-drag calipers

Ventilated rotor-

a motor that has cooling fins cast between the braking surfaces to increase the cooling area of the rotor

Proportioning valve-

a pressure reduction valve used in the rear brake circuit

Coefficient of Friction (COF)-

a relative measurement of the friction developed between two objects in contact with each other

Combination valve-

an H-valve, used in some early air-conditioning systems, combining a suction throttling valve and an expansion valve