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CDL Common Questions > 80 Air Brake Questions > Flashcards

80 Air Brake Questions Flashcards

1
Q

Oil and water usually collect in compressed air
tanks. If you d on o t have a n automatic tank drain, when should you drain the air tanks?

A

After every working day

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2
Q

To check the slack adjusters on S c a m brakes, you should

A

Park on level ground, chock the wheels, and release the parking brakes

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3
Q

The safety valve is set to automatically reduce pressure at ___ psi

A

150

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4
Q

If your truck has a properly functioning dual air brake system and minimum-size air tanks, the air pressure should build from 85 to 100 psi within __ seconds.

A

45

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5
Q

During normal driving, spring brakes are usually held back by

A

Air pressure

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6
Q

The driver must be able to see a warning before the pressure in the service air tanks falls below __ psi.

A

60

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7
Q

Excessive use of the service brakes results in overheating, which can lead to

A

Expansion of the brake drums

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8
Q

When you are going down a long or steep grade after selecting the proper gear, the proper method of braking is to brake until your speed is about ___ miles
per hour below your «safe» speed and then release your brakes.

A

5

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9
Q

The air brake lag distance at 55 mph on dry. pavement adds about __ feet.

A

32

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10
Q

How can you check the slack adjusters?

A

Park on level ground, turn off the parking brakes, and pull had on each slack adjuster. It shouldn’t move more than one inch

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11
Q

The total stopping distance for air brakes is longer than that for hydraulic brakes because of

A

Brake lag

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12
Q

Repeatedly pressing and releasing (fanning) the brake pedal m a y result in

A

A loss of brake air pressure

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13
Q

The parking or emergency brake on a heavy vehicle can only be held in position by something that cannot leak away, like

A

Spring pressure

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14
Q

Air braking takes more time than hydraulic braking because air

A

Takes more time to flow through the lines than hydraulic fluid

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15
Q

When you apply the brakes, the brake shoes/linings are pressed against the

A

Brake drum

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16
Q

It is not safe to drive a vehicle that has brake drums with cracks that are longer than __ of the width of the friction area.

A

1/2

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17
Q

The emergency brake system

A

Uses parts of the service brake and parking brake systems to stop the vehicle in the event of a brake system failure.

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18
Q

What is a dual air brake system?

A

A two-brake system; one brake operates the front brakes and one operates the back brakes

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19
Q

Before starting down a hill, you should be in the proper gear

A

So you only have to apply the brake just hard enough to feel a definite slowdown

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20
Q

The driver must be able to see a low pressure
warning, which comes on before pressure in the service air tank falls below___ psi.

A

60

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21
Q

Modern air brake systems are three different systems combined: the service brakes, parking brakes, and ___ brakes

A

Emergency

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22
Q

The air supply pressure gauge shows how much pressure

A

Is in the air tanks

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23
Q

The parking or emergency brakes of trucks or buses can legally be held by __ pressure.

A

Spring

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24
Q

The stop light switch

A

Turns on the brake lights to warn drivers behind you.

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25
Q

With air brake-equipped vehicles, the parking brakes should be used

A

Whenever you leave the unattended

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26
Q

For air brake systems in good condition, the air compressor should start pumping at about __ psi.

A

100

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27
Q

An air brake system is fully charged at __ psi.

A

125

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28
Q

The air compressor governor controls

A

When air is pumped into the air storage tanks

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29
Q

If your vehicle has an alcohol evaporator, every day during cold weather, you should

A

Check and fill the alcohol level

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30
Q

Emergency controlled braking is when you

A

Apply the brakes as had as you can without locking the wheels

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31
Q

Water should be drained from the compressed air tanks

A

Because water can freeze in cold weather and cause brake failure

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32
Q

What is the danger of non-functioning low pressure warning signal?

A

This could cause sudden emergency braking in a single-circuit air system

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33
Q

You know that your brakes are fading when

A

You have to press the brake pedal harder to control speed on a downgrade

34
Q

Tractor and straight truck spring brakes will come fully on when the air pressure drops to a range of __ psi.

A

20 to 45

35
Q

Your truck has a dual air system, and one of the systems loses its pressure. What will happen?

A

Either the front or rear brake will not be fully operational

36
Q

If your truck or bus has dual parking control valves, you can use pressure from a separate tank to

A

Release the spring emergency/parking brakes to move a short distance

37
Q

The most common type of foundation brake found on heavy vehicles is the

A

S-cam drum

38
Q

If you must make an emergency stop, brake so that you

A

Can steer and you vehicle will stay in a straight line

39
Q

The brake system that applies and releases the brakes when the driver presses the brake pedal is the __ brake system.

A

Service

40
Q

The brake pedal in an air brake system

A

Controls the air pressure applied to the brakes

41
Q

To engage the parking brakes under normal conditions, the driver must first

A

Let the air out of the spring brakes

42
Q

Air tanks must be drained

A

To drain moisture and oil out of the tanks

43
Q

What are spring brakes?

A

If the air brakes leak down, springs apply the brakes to stop the vehicle

44
Q

The use of air brakes on a downgrade is only a supplement to the

A

Braking effect of the engine

45
Q

When you apply the brakes by pushing down on the brake pedal,

A

Air pressure is applied to the brake pads

46
Q

What is a slack adjuster?

A

It is an adjusting nut on the backside of the brake drum, used for adjusting the brakes

47
Q

Air-brake equipped vehicles have

A

An air supply pressure gauge

48
Q

To test the static air leakage rate, you should

A

Turn off the engine, release all brakes, and let the system settle

49
Q

When is it OK to leave your truck unattended without applying parking brakes or chocking the wheels?

A

Never

50
Q

What factors can cause brakes to fade or fail?

A

Overheating, low air pressure, and not relying on the engine braking effect

51
Q

If oil and water collects in the air tanks, what could happen to the brakes?

A

The brakes could fail

52
Q

To correct a drive-wheel braking skid, you should

A

Stop braking, turn quickly, and counter steer

53
Q

You are on a steep downgrade and have reached your safe speed of 4 0 mph. You would apply the service brakes until your speed drops to __ mph

A

35

54
Q

Some air brake systems have an alcohol evaporator. What may happen if you don’t keep the unit filled with alcohol?

A

Ice may form in the air storage tanks and cause the brakes to fail

55
Q

Before you drive a truck or bus with a dual air
brake system, the pressure in each air brake system should be at least __ psi.

A

100

56
Q

If pressure is not built up fast enough,

A

The air pressure may drop too low during driving

57
Q

When you pull hard on a slack adjuster, if its free play is more than __, the slack adjuster will need to be adjusted.

A

1 inch

58
Q

How should you check that the spring brakes come on when the air pressure in the system drops below a certain level?

A

Park on level ground, chock the wheels, release the parking brake when you have enough air pressure, shut the engine off, and repeatedly press and release the brake pedal

59
Q

In air brake vehicles, the parking brakes should be used

A

Anytime the vehicle is parked

60
Q

To make an emergency stop with air brakes, using the stab braking method, you should

A

Press on the brake pedal as hard as you can, release the brakes when the wheels lock, and apply the brakes again when the wheels start to roll

61
Q

If the air compressor should develop a leak, what keeps the air in the tanks?

A

The one-way check valve

62
Q

The application pressure gauge shows how much pressure you have

A

When you are applying the brakes

63
Q

The braking power of the spring brakes

A

Depends on the service brakes being in adjustment

64
Q

It is accepted that too much heat caused by using your brakes too often can also cause

A

Brake fade or failure

65
Q

The S-cam

A

Forces the brake shoes against the inside of the brake drum

66
Q

Converter dollies built on or after March 1, 1998 are required to have anti-lock brakes. These dollies will have

A

A yellow malfunction lamp on the left side of the dolly

67
Q

If the spring brakes are on, when should you push the brake pedal?

A

Never

68
Q

What is the first thing you should do when a low air pressure warning comes on?

A

Stop and safely park as soon as possible

69
Q

In ideal conditions, a truck or bus equipped with an air brake and traveling at 55 mph would require what stopping distance?

A

More than 450 feet

70
Q

What do air brakes use to make the brakes work?

A

Compressed air

71
Q

The parking brake applies and releases

A

The parking brakes when you use the parking brake control

72
Q

The S-cam forces the brake shoes away from one another and presses them against the inside of the brake drum. It is called the S-cam because

A

It is shaped liked the letter «S»

73
Q

How can you test the low pressure warning signal?

A

Shut off the engine with enough air pressure, turn on the electrical power, and step on and off the brake pedal until the low air pressure warning signal comes on

74
Q

What is the purpose of an alcohol evaporator?

A

To reduce the risk of ice in the brake valves and other parts in cold weather

75
Q

The brake chamber fills with air, pushing the ro
out, which moves the ___, which twists the ___.

A

Slack adjuster; brake camshaft

76
Q

To test the air service brakes,

A

Brake firmly while slowly moving forward

77
Q

Which is the most important thing to remember about emergency braking?

A

If the wheels are skidding, you cannot control the vehicle

78
Q

Controlled braking

A

Is used to keep a vehicle in a straight line when braking

79
Q

The air loss rate for a straight truck or bus witt the engine off and the brakes on should not be more than

A

3 psi in one minute

80
Q

The air compressor stops pumping air at ___ psi

A

125

CDL Common Questions (2 decks)

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