Deck 6: Power Brake Systems

Question 1

Technician A says the rear or back of the booster is that part nearest the driver and abuts the bulkhead. Technician B says the front or forward part of the booster is where the master cylinder is installed. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Answer 1

C

Question 2

A vehicle has power assist during engine operation, but it has no assist after the engine has been off and during initial engine startup. Technician A says a stuck close vacuum check valve could be the cause. Technician B says a leaking vacuum check valve could be the cause. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Answer 2

B

Question 3

Technician A says pedal free play is the first easy movement of the brake pedal before the braking action begins to engage. Technician B says pedal free play should only be about 1/16 to 3/16 on most cases. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Answer 3

C

Question 4

Vacuum power brakes are being discussed. Technician A says vacuum on both sides of the diaphragm doubles the amount of force on the master cylinder pistons. Technician B says the return spring forces the diaphragm to the forward position when there is vacuum on both sides of the diaphragm. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 5

Technician A says to diagnose a brake system that does not release, loosen the connection between the master cylinder and the brake booster. Technician B says if the brakes do not release when the master cylinder is removed from the booster, the booster is defective. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 6

Electrohydraulic brakes are being discussed. Technician A says an electrohydraulic brake system controls hydraulic braking action through the use of electrical solenoids. Technician B says the system shares information with ABS, TCS, and electronic suspension. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 7

Technician A says the tool shown is used to adjust the booster's vacuum valve. Technician B says the tool is used to set the depth of the booster's diaphragm. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 8

All of the following statements about hydro-boost system accumulators are true EXCEPT:

A)the accumulator is spring loaded or charged with pressurized fluid.
B)accumulators hold a charge of pressurized fluid as a reserve if fluid flow from the steering pump is lost or reduced.
C)accumulators are only pressurized when the pump flow stops.
D)the fluid compresses an internal piston and spring or a gas charge.

Question 9

Technician A says, with the brakes off, the pressure in the front chamber helps hold the diaphragm in the released position. Technician B says air pressure in the rear chamber counteracts the opposing vacuum to hold the diaphragm in the released position. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 10

Technician A says a hydraulic brake booster is usually found on vehicles with diesel engines. Technician B says most passenger cars and light trucks use the hydro-boost system. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 11

Technician A says the air and vacuum valves used on a tandem diaphragm must control vacuum and atmospheric pressure on two diaphragms at the same time. Technician B says when the brakes on a tandem diaphragm system are released, there is a vacuum on both sides of each diaphragm. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 12

Technician A says all vacuum boosters are single-diaphragm units. Technician B says vacuum boosters can have one or two diaphragms, and single-diaphragm boosters are smaller in diameter than dual-diameter diaphragm vacuum boosters . Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 13

Technician A says hydro-boost operation can be divided into three stages. Technician B says that moderate brake application causes the input pushrod to press on the reaction rod in the end of the power piston. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 14

Technician A says lever-type vacuum power-assist brake system gives the driver a "feel" for the braking effort. Technician B says this "feel" is similar to that of a nonpower boost brake system. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 15

Technician A says a hydraulic power booster unit is installed in the same place as a vacuum booster. Technician B says the function of the hydraulic power booster is to multiply the force of the driver's foot on the brake pedal. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 16

Technician A says a restricted vacuum feed hose may cause loss of assist after several quick brake applications. Technician B says brake fluid in the vacuum feed hose indicates a leaking master cylinder seal. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 17

On a vacuum-boosted system, all of the following can cause poor power-assist unit operation EXCEPT:

A)excessive manifold vacuum.
B)leaking or collapsed vacuum lines.
C)punctured diaphragm.
D)leaky piston seals.

Question 18

Technician A says vacuum for most power brake systems is supplied by the engine intake manifold. Technician B says many late-model cars that use intake manifold vacuum as the power source for the power brakes have a vacuum reservoir. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 19

Technician A says a ir fills the rear chamber when brake application opens the air valve and closes the vacuum valve, and the front chamber is kept in vacuum . Technician B says w hen the brakes are held at midpoint, both valves are closed to trap vacuum and atmospheric pressure and keep the diaphragm in a balanced position . Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 20

All of the following are types of vacuum boosters EXCEPT:

A)tandem booster with reaction disc.
B)tandem booster with reaction lever.
C)single diaphragm with reaction lever.
D)single diaphragm with reaction disc.

Question 21

Technician A says that energy can be stored by a spring in an accumulator. Technician B says that energy can be stored by gas under pressure in an accumulator. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 22

Technician A says except for the master cylinder pushrod adjustment, vacuum and hydraulic power-assist units are not adjusted in normal service. Technician B says if the booster is suspect, it is removed with a new or rebuilt unit, or it can be rebuilt in the shop. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 23

A vehicle equipped with a vacuum brake booster has no power-assisted stops with the engine off but operates normally with the engine running. Which of the following is the most likely cause?

A)A leak in the booster diaphragm
B)A leak in the hose from the intake manifold
C)A leaking check valve
D)A leak in the hydraulic system

Question 24

Technician A says the hydro-boost fluid reservoir for the pump may be remote from the pump location. Technician B says the  controller, master cylinder, pump, and reservoir are included in a single unit. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 25

Describe a spool valve and how it works.

Question 26

In the event that the vacuum source fails what prevents the loss of braking operation on a power brake system?

Question 27

The _________ tells the electrohydraulic controller how fast and how far the brake pedal has been applied to judge the driver's needs.

A)master cylinder module
B)EHB control module
C)vacuum booster
D)stroke sensor

Question 28

Electro-hydraulic brakes are being discussed. Technician A says these systems use a vacuum booster. Technician B says these systems share information with other electronic systems. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 29

What is the purpose of brake assist (BA)found on some vacuum boosters?

Question 30

Technician A says some types of problems in the steering system can affect the hydro-boost system. Technician B says some types of problems in the hydro-boost system can affect the steering system. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 31

The diaphragm _______ returns the diaphragm and power piston to the unapplied position when brakes are released?

A)residual vacuum
B)residual atmospheric pressure
C)return spring
D)tension

Question 32

What is the purpose of a vacuum reservoir?

Question 33

If pedal height adjustment is needed, the first step is to:

A)turn the pushrod in or out as necessary.
B)loosen the pushrod locknut.
C)tighten the locknut.
D)recheck the height.

Question 34

Servicing a system with EHB is being discussed. Technician A says servicing these systems is no different from servicing conventional systems. Technician B says some EHB systems have no vacuum booster. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 35

Technician A says that diesel engines do not create a vacuum in their intake manifold. Technician B says most diesel engines use hydraulically assisted power brake boosters, and the pressure for the assist is developed in the power steering pump on some diesel engines. Who is correct?

A)A only
B)B only
C)Both A and B
D)Neither A nor B

Question 36

Explain how the vacuum valve is constructed.

Question 37

List the five stages of vacuum booster operation.

Question 38

What are valleys?

Question 39

What is the purpose of the vacuum check valve?

Question 40

During removal of a vacuum booster, the master cylinder should be:

A)removed completely from the vehicle.
B)removed from the booster and moved aside.
C)disconnected from the lines and removed with the booster.
D)disconnected from the firewall.

Question 41

A spool valve is used to direct flow to the power chamber in the ______________ hydraulic power brake system.

Question 42

Integral ABS systems combine the master cylinder, electric pump motor, and hydraulic modulator into one unit.

Question 43

Power brakes are simply conventional brakes with an added power booster.

Question 44

In a booster with a reaction disc, the input pushrod and vacuum valve plunger bear on a ____________________ .

Question 45

____________________ refers to two or more devices placed one behind the other in line.

Question 46

The hydro-boost power braking system uses DOT 3 or DOT 4 brake fluid as specified by the carmaker.

Question 47

Loss of hydraulic power from the hydro-boost means the driver loses all braking ability.

Question 48

Cars with diesel engines have excessively high intake manifold vacuum.

Question 49

A spool valve controls fluid flow through the hydro-boost pressure supply pump.

Question 50

______________ is simply air pressure below atmospheric pressure.

Question 51

Booster pushrod adjustment is usually checked with a gauge, which measures from the end of the pushrod to the booster shell. Two basic gauge designs are used: ____________________ and ____________________.

Question 52

The vacuum power booster requires vacuum and air at atmospheric pressure to operate.

Question 53

Two 10-square-inch diaphragms can provide the same power as one 40-square-inch diaphragm.

Question 54

During a panic stop on a vehicle equipped with vacuum boost system and brake assist, less assist will be provided to prevent wheel lock-up.

Question 55

______________ ABS systems combine the master cylinder, electric pump motor, and hydraulic modulator into one unit .

Question 56

Intake manifold vacuum decreases and increases as the engine is accelerated and decelerated.

Question 57

Vacuum boosters generate their application energy through the ____________________ between engine vacuum and atmospheric pressure.

Question 58

Explain how integral antilock brake systems provide brake assist.

Question 59

The air system for a vacuum booster consists of a(n) ____________________ and air filter.

Question 60

Describe the booster diaphragm in vacuum booster construction.

Question 61

The ______________ valve is the vacuum booster valve that controls atmospheric pressure on the vacuum diaphragm.

Question 62

During normal operation of the EHB, the master cylinder supplies ______________ fluid to the modulator.

Question 63

______________ power brakes are by far the most common kinds of power brakes.