Air Brake Test

Front 1

An internal combustion engine must convert its ________ into _________.

Back 1

heat energy; mechanical energy.

Front 2

The final factor that moves the vehicle is the ______________.

Back 2

amount of traction its tires have on the road surface.

Front 3

Friction is the force that resists ________________.

Back 3

movement between two surfaces in contact with each other

Front 4

To stop a vehicle, the ________ are forced against the machined
surfaces of the brake drums, creating ______, which in turn creates ______.

Back 4

brake shoe linings; friction; heat

Front 5

The engine converts the energy of ____ into the energy of _____; the brakes must ___________.

Back 5

heat; motion; convert this energy of motion back into the energy of heat.

Front 6

The amount of heat the brake drums
can absorb depends on _________.

Back 6

the thickness of the metal

Front 7

The final factor that stops the vehicle is ________________.

Back 7

the traction between the tires and the road surface.

Front 8

When enough ________ is created between ______________, the wheels stop turning.

Back 8

friction; the brake lining and the drums

Front 9

To stop the vehicle in 1/10 the time it took to accelerate would require a stopping force of __________.

Back 9

10 times the acceleration force

Front 10

Most brake linings operate best at around ____°C and should not exceed ____ °C.

Back 10

250, 425

Front 11

The distance required to stop a vehicle depends on its ____ and _______, in addition to energy, heat and friction.

Back 11

speed; weight

Front 12

The distance required to stop a vehicle depends on its speed and weight, in addition to _____, _______, and _______.

Back 12

energy, heat and friction

Front 13

The braking force required to stop a vehicle varies directly with its _____ and ______.

Back 13

weight; speed

Front 14

If the weight is doubled, the braking force must be _______ to be able to stop in the same distance.

Back 14

doubled

Front 15

If the speed is doubled, the braking force must be ____________ to be able to stop in the same distance.

Back 15

increased four times

Front 16

When weight and speed are both doubled, the braking force must be ________to be able to stop in the same distance.

Back 16

increased eight times

Front 17

Braking systems use devices to gain a(n) _______ advantage. The most common device for this purpose is _________.

Back 17

mechanical; leverage

Front 18

If compressed air of 120 psi acts on a diaphragm of 30 square inches, _____lb of force is produced.

Back 18

3,600

Front 19

Stopping distance consists of three factors:

Back 19

• driver’s reaction time
• brake lag
• braking distance

Front 20

Driver’s reaction time: Reaction time is often called _________.

Back 20

“thinking time”

Front 21

How long is typical driver reaction time?

Back 21

3/4 of a second

Front 22

Define "brake lag."

Back 22

the time it takes the air to travel through a properly maintained air brake system

Front 23

Define braking distance:

Back 23

The actual distance the vehicle travels after the brake is applied until the vehicle stops.

Front 24

Brakes must be used keeping in mind
_____________.

Back 24

the heat generated by friction.

Front 25

A basic air brake system capable of stopping a vehicle has which 5 main components?

Back 25

1. A compressor to pump air with a governor to control it.

2. A reservoir or tank to store the compressed air.

3. A foot valve to regulate the flow of compressed air from the reservoir when it is needed for braking.

4. Brake chambers and slack adjusters to transfer the force exerted by the compressed air to mechanical linkages.

5. Brake linings and drums or rotors to create the friction required to stop the wheels.

Front 26

________ is used to transmit force in an air brake system.

Back 26

compressed air

Front 27

A compressor is designed to ________which results in pressurized air.

Back 27

pump air into a reservoir

Front 28

In an airbrake system, the compressor is driven by __________,

Back 28

the vehicle’s engine

Front 29

A governor controls _________ in the system by controlling when the compressor pumps air. This is known as the ________ or _________ stage.

Back 29

the minimum and maximum air pressure

“loading” or
“unloading”

Front 30

Most compressors have _____ cylinders.

Back 30

2

Front 31

The compressor must be able to build reservoir air pressure from ___ to ____ psi within _____ minutes. Otherwise .....

Back 31

50
90
three minutes
compressor requires servicing

Front 32

A compressor may not be able to build air pressure from 50 to 90 psi within three minutes if ________ or if ___________,

Back 32

the air filter is plugged
if the belt was slipping

Front 33

It is very important the air that enters the system __________.

Back 33

be kept as clean as possible

Front 34

Usually compressors are lubricated _____________, although some compressors are __________ and require ____________.

Back 34

from the engine lubrication system; self–lubricating; regular checks of the lubricant level

Front 35

Placing the compressor in the unloading stage is done by __________, holding them open, allowing the air to be _____________,
instead of compressing the air.

Back 35

directing air pressure to the inlet valves of the compressor

pumped back and forth between the two cylinders

Front 36

How is a plugged air filter likely to affect the air compressor?

Back 36

restrict the flow of air into the compressor, reducing its efficiency

Front 37

A piston type compressor operates on the same principle as _______________ of an engine.

Back 37

the intake and compression strokes

Front 38

T or F
Air brake vehicles are equipped with more than one reservoir.

Back 38

True

Front 39

The first reservoir after the compressor is referred to as the _______ or ______ reservoir. The other reservoirs are known as ________ and ______ OR ______ reservoirs.

Back 39

supply or wet
primary and secondary
dry

Front 40

When air is compressed, it becomes _____.

Back 40

hot

Front 41

The heated air cools in the reservoir,
forming ____________.

Back 41

condensation

Front 42

How does sludge accumulate at the bottom of the reservoir?

Back 42

oil leaks past the piston rings of the compressor and mixes with the moisture caused by condensation

Front 43

Reservoirs are equipped with ________ so that any moisture or sludge that may have accumulated can be .

Back 43

drain valves; drained

Front 44

What should you look for when draining the airbrake system?

Back 44

sludge

Front 45

To minimize the amount of water collection, all reservoirs must be _________.

Back 45

drained daily

Front 46

To drain the reservoirs always start with __________.

Back 46

the wet reservoir on the tractor

Front 47

Some reservoirs may be equipped with _______, also known as splitter valves. Describe what they do.

Back 47

automatic reservoir drain valves; automatically exhaust moisture from the reservoir when required,

Front 48

A(n) _________ may be installed between the _________ and the _________ to help remove moisture from the compressed air.

Back 48

air dryer; compressor;wet reservoir

Front 49

Air dryers use _________ to purge or eject the accumulated contaminants from their desiccant bed.

Back 49

air pressure

Front 50

In an air dryer, the purge valve has ___________, which prevents
the moisture from freezing in cold climate operation. What should be checked w.r.t. this system?

Back 50

a heater element
The wiring connected to the heater should be inspected for loose or disconnected wires.

Front 51

A safety valve protects reservoirs from _________ and ________if the governor malfunctioned and did not place the compressor in the _________.

Back 51

becoming over pressurized and bursting; unloading stage

Front 52

A safety valve is normally set at ____ psi.

Back 52

150

Front 53

The ________ is the means of applying air to operate the brakes.

Back 53

foot–operated valve

Front 54

The foot–operated valve is the means of __________________.

Back 54

applying air to operate the brakes

Front 55

Releasing the treadle allows the application air to be ___________.

Back 55

released through the exhaust ports into the atmosphere

Front 56

When the driver applies the brakes, depressing the treadle part way, the foot valve will automatically _____________.

Back 56

maintain the application air pressure without the driver having to adjust the pressure of his foot on the treadle

Front 57

A brake chamber is a circular container
divided in the middle by _________.

Back 57

a flexible diaphragm

Front 58

Front brake chambers are usually smaller than those in the rear because __________________.

Back 58

front axles carry less weight

Front 59

A brake chamber is usually mounted _________, near the ___________.

Back 59

on the axle; wheel that is to be equipped for braking

Front 60

The slack adjuster adjusts ________ in the linkage between ________ and _________. This occurs as _________.

Back 60

the free play; the push rod; the brake shoes; the brake linings wear

Front 61

On manual slack adjusters, the adjusting worm bolt is turned until the ____________ and then _________.

Back 61

brake linings touch the drums; backed off

Front 62

A locking device, which may be a spring loaded collar over the head of the adjusting bolt, must be depressed when the wrench is slipped over the bolt head. This is
known as ____________.

Back 62

a positive lock slack adjuster

Front 63

Two types of manual slack adjusters

Back 63

positive lock; ball indent

Front 64

Vehicles rarely “lose” their brakes because of air loss; it is usually
because they are _________.

Back 64

out of adjustment

Front 65

Some systems have ________ that adjust automatically to compensate for brake lining wear, usually maintaining the correct clearance between the _______ and _________.

Back 65

automatic slack adjusters; brake lining; drum

Front 66

A ___________ is designed to pump _____ into a ______ which results in pressurized air.

Back 66

compressor; air; reservoir

Front 67

T or F
Whenever the engine is running, so is the compressor.

Back 67

T

Front 68

When pressure in the system is adequate, anywhere from a low of ____ psi to a high of ____ psi it is not necessary for the compressor to pump air.

Back 68

80; 135

Front 69

A _________ controls the minimum and maximum air pressure in the system by controlling when the ________________.

Back 69

governor; compressor pumps air

Front 70

Most compressors have ____ cylinders.

Back 70

2

Front 71

When the system pressure reaches its maximum, which is between ________, the governor places the compressor in the _______ stage.

Back 71

115 and 135 psi; “unloading”

Front 72

The __________ must be able to build reservoir air pressure from 50 to 90 psi within _______ minutes.

Back 72

compressor; 3

Front 73

2 types of automatic slack adjusters

Back 73

stroke–sensing or clearance–sensing

Front 74

A stroke–sensing adjuster will adjust
the slack when it ___________.

Back 74

senses the set stroke is exceeded

Front 75

A clearance–sensing adjuster will adjust when the proper clearance between ___________ is not maintained.

Back 75

the brake drum and brake shoe

Front 76

If a vehicle is equipped with automatic slack adjusters, it should not be taken for granted that ___________.

Back 76

the brakes will always be in adjustment

Front 77

Two most common problems with automatic slack adjusters:

Back 77

excessive premature wear; internal
contamination.

Front 78

A compressor may not be able to build air pressure from 50 to 90 psi within three minutes if (3 things) . . .

Back 78

1. the air filter is plugged
2. if the belt was slipping
3. compressor could be faulty.

Front 79

Usually compressors are lubricated from ___________.

Back 79

the engine lubrication system,

Front 80

What are the five basic components of an air brake system?

Back 80

-compressor/governor
-reservoir
-foot valve
-brake chambers and slack adjusters
-brake linings and drums/rotors

Front 81

At what pressure should the governor cause the compressor to return to its “loading” stage?

Back 81

80 psi

Front 82

At what pressure will the governor place the compressor in the “unloading” stage?

Back 82

135 psi

Front 83

How is a plugged air filter likely to affect the air compressor?

Back 83

compressor may not be able to build air pressure from 50 to 90 psi within three minutes

Front 84

What causes moisture to form in the air brake system?

Back 84

compressed becomes hot; heated air cools in the reservoir forming condensation

Front 85

When is the compressor able to accomplish most of its cooling?

Back 85

during the unloading stage

Front 86

How are most compressors lubricated?

Back 86

from the engine's lubrication system

Front 87

How often should the reservoirs be drained?

Back 87

daily

Front 88

Is it necessary to allow all the pressure to escape from the reservoir in order to remove the moisture and sludge which may have accumulated?

Back 88

yes

Front 89

What is the maximum pressure available for a full brake application at any given time?

Back 89

between 115 and 135 psi

Front 90

What will result if the brake drums are worn thin or turned too far?

Back 90

heat will build up too quickly

Front 91

If the governor valve failed to “unload” the compressor, what would protect the reservoirs from becoming over pressurized and bursting?

Back 91

a safety valve

Front 92

What is the purpose of having more than one reservoir?

Back 92

gives system a larger volume of main reservoir air

Front 93

What are two functions of the slack adjusters?

Back 93

1. translates chamber's linear motion into rotary motion to apply and release S-cam brake
2. provides a mechanism to adjust the brake as the linings wear

Front 94

Does the amount of slack in the brake linkages have any effect on the braking efficiency of the vehicle?

Back 94

yes

Front 95

What is the advantage of keeping the brake chamber push rod travel adjusted within limitations?

Back 95

so there is enough push rod travel to compensate for drum expansion

Front 96

What is the most common cause of loss of effective braking in an air brake system?

Back 96

system out of adjustment

Front 97

Do automatic slack adjusters on S–cam brakes require checking?

Back 97

yes

Front 98

Can the adjustment on air–operated disc brakes differ from S–cam brakes?

Back 98

yes, they have different specifications

Front 99

What occurs when drum brakes become overheated?

Back 99

heated drums expand away from brake lining requiring greater push rod travel

Front 100

What causes brake fade?

Back 100

If a brake is out of adjustment there would not be enough reserve stroke of the push rod travel to compensate for drum expansion.

Front 101

What is the main function of the foot valve?

Back 101

it is the means of applying air to operate the brakes

Front 102

Why does the “feel” of an air–operated foot valve differ from a hydraulic brake pedal?

Back 102

they are spring loaded

Front 103

On what principle does a disc brake operate?

Back 103

A power screw works like a C–clamp, so that the lining pads exert equal force to both sides of the disc or rotor.

Front 104

What type of air–over–hydraulic brake system requires the operator to hold an air brake endorsement?

Back 104

an air–actuated hydraulic brake system

Front 105

Vehicles rarely “lose” their brakes because of air loss; it is usually
because . . .

Back 105

they are out of adjustment

Front 106

It's important to understand that the power needed to stop generates ________ which could create what problem?

Back 106

heat: damage the brakes

Front 107

The governor must place the compressor in the "loading" stage at no lower than ____ psi.

Back 107

80

Front 108

The "unloading" stage allows the compressor to _______.

Back 108

cool

Front 109

The purpose of reservoirs is _________.

Back 109

to hold a supply of compressed air

Front 110

The air pressure initiated by the foot valve operation will not exceed _________.

Back 110

the air pressure in the reservoir

Front 111

The governor must place the compressor in the "loading" stage at no lower than ____ psi.

Back 111

80

Front 112

Air treadles are __________, producing a different "feel" from hydraulic brake applications.

Back 112

spring loaded

Front 113

The pressure on the push rod in a brake chamber is dependent on what 2 factors?

Back 113

the air pressure and the diaphragm size

Front 114

The slack adjuster converts the _______ motion of the push rod from the brake chamber to a ________ motion of the brake camshaft and ______.

Back 114

pushing; twisting; S-cams

Front 115

If slack adjusters are not adjusted within the limitations, _______ is reduced and _______ is increased.

Back 115

effective braking; brake lag time

Front 116

Automatic slack adjusters are either ________ or ________.

Back 116

stroke-sensing; clearance-sensing

Front 117

A stroke-sensing slack-adjuster will adjust the slack when it senses that ________.

Back 117

the set stroke is exceeded

Front 118

A clearance-sensing adjuster will adjust when the proper clearance between the ________ and ______ is not maintained.

Back 118

brake drum;brake shoe

Front 119

A number of _________ above _____ psi are required to keep automatic slack adjusters in adjustment.

Back 119

full brake applications; 90

Front 120

Fading or reduction in braking effort occurs when the __________ expand away from the _______.

Back 120

heated drums; brake linings

Front 121

brake linings lose their effectiveness with _______.

Back 121

overheating

Front 122

Air-over-hydraulic brake systems were developed fro medium weight vehicles because: (3)

Back 122

1. diesel engines do not have a source for vacuum boosting unless equipped with a vacuum pump)
2. medium weight vehicles to not require a full air brake system
3. gives the option of pulling an air brake equipped trailer

Front 123

Two types of air-over-hydraulic brake systems:

Back 123

air-actuated; air-boosted

Front 124

What type of air–over–hydraulic brake system requires the operator to hold an air brake endorsement?

Back 124

air-actuated

Front 125

Two advantages of hydraulic brake systems:

Back 125

1. reliable self-adjusters
2. limited maintenance

Front 126

The air pressure gauge shows the pressure in ___________, not the ________.

Back 126

dry reservoirs, wet reservoir

Front 127

Common operating pressures of air brakes are _____ psi to ____ psi.

Back 127

80;135

Front 128

A low pressure warning device typically activates around ____ psi.

Back 128

60

Front 129

What must the driver do when low pressure warning system activates?

Back 129

stop the vehicle in a safe place immediately and find the cause of the air loss

Front 130

At 60 psi, expect that your _______ are partially applied.

Back 130

spring parking brakes

Front 131

The stop light switch is an _______ electric switch that turns on brake lights at the rear of the vehicle when a brake application is being made.

Back 131

air-operated

Front 132

What is the purpose of a quick release valve?

Back 132

allows the brakes to release quickly by fully discharging the application air near the brake chambers

Front 133

What is the purpose of the relay valve?

Back 133

Corrects the condition of "brake lag" with long wheel base vehicles.

Front 134

For better steering control on when braking on a slippery road surface, it can be an advantage to ________.

Back 134

reduce the braking effort to the front wheels

Front 135

When should a driver use the front brake limiting valve?

Back 135

on slippery surfaces

Front 136

How is "brake lag" to the rear wheels minimized?

Back 136

with a relay valve

Front 137

In the spring parking brake system, the brakes are applied by ________ and retracted by ________.

Back 137

spring pressure; air pressure

Front 138

The effectiveness of the spring parking brake depends on the ________ adjustment.

Back 138

service brake

Front 139

Loss of air from the system may automatically ________.

Back 139

apply the brakes

Front 140

Any time the reservoir pressure drops to approximately _____ psi, the parking brake valve will close automatically, placing the spring brakes into full application.

Back 140

35

Front 141

How are parking brakes held in the released position?

Back 141

with air pressure

Front 142

What is meant by "compounding" the brakes?

Back 142

Applying full-brake application while the parking brake is applied.

Front 143

On the pre-trip brake inspection it is important to make sure that the parking brake spring is not _______ or it will not expand and apply the brake.

Back 143

manually caged

Front 144

It take approximately ____ psi of air pressure to keep the parking brake springs caged.

Back 144

90

Front 145

Caution: Parking brakes should _______ before making a service brake application.

Back 145

be in the release position

Front 146

The speed at which the spring brakes will stop the vehicle depends on what four factors:

Back 146

1. weight and speed of vehicle
2. steepness of grade
3. spring force of the brakes
4. adjustment of the service brakes

Front 147

If the brakes are overheated, care must be taken when _____________.

Back 147

parking the vehicle

Front 148

Do not set the spring parking brakes until you have verified that the brake drum is _______.

Back 148

cool to the touch

Front 149

Procedure for parking a vehicle with overheated brakes:

Back 149

park on level ground, stop the engine, leave the transmission in lowest gear, and block the wheels

Front 150

Why are spring brakes a reliable type of parking brake?

Back 150

They are not dependent on the air system.

Front 151

What are the functions of the cab-mounted parking brake control valve?

Back 151

exhaust air out of the spring parking brake circuit to apply brakes, or pressurize the circuit to release them

Front 152

How can some types of parking brakes be released without the use of air pressure?

Back 152

they can be released mechanically by "winding them off" of "caging" them

Front 153

What is the danger of disassembling a spring parking brake unit?

Back 153

springs are under extreme pressure

Front 154

Why would you have to "cage" the spring parking brake?

Back 154

If all air is lost the vehicle must be towed.

Front 155

What is the reason for releasing the parking brakes before making a full brake application test?

Back 155

you don't want to "compound" the brakes

Front 156

Will parking brakes apply "automatically" in all braking systems?

Back 156

No. Some systems have "blue button" that applies only tractor brakes and not trailer brakes.

Front 157

What is the purpose of a two–way check valve?

Back 157

to direct air flow into a common line from either of two sources

Front 158

Why should the glad hands be protected when not in use?

Back 158

don't want dirt or water in the lines; don't want lines chafing against vehicle components

Front 159

How can a driver control the trailer brakes independently?

Back 159

by the trailer brake hand valve

Front 160

Should the hand valve be used for parking?

Back 160

no

Front 161

What is the purpose of the tractor protection valve?

Back 161

to prevent a total loss of air from the tractor if the trailer breaks away, or it the connecting lines fail

Front 162

How can you test the proper function of the tractor protection valve?

Back 162

see procedure on page 43

Front 163

What is the purpose of the trailer supply valve?

Back 163

permits reservoir air pressure to flow through to the trailer - also opens the tractor protection valve

Front 164

Name three functions of the relay emergency valve.

Back 164

1. Relays air from the trailer reservoir to the trailer brake chambers during a brake application
2. Directs trailer reservoir air pressure to the trailer brakes, causing an emergency application of the brakes.
3. Stops air pressure in the trailer reservoir from going back to the tractor (one-way check valve).

Front 165

Describe the functions of the supply (emergency) line (2)

Back 165

charges the trailer reservoir; loss in pressure causes emergency braking of the trailer

Front 166

Describe the function of the control (service) line.

Back 166

supplies application air to the trailer brakes (control pressure)

Front 167

What will occur if the supply (emergency) line ruptures?

Back 167

The sudden loss of air pressure in the supply (emergency) line will trigger the relay emergency valve which causes the trailer reservoir to dump its air directly to the trailer brake chambers.

Front 168

What will occur if the control (service) line ruptures?

Back 168

No action will take place until a brake application is made.

Front 169

What will occur if a brake application is made with a ruptured control (service) line?

Back 169

No action will take place until a brake application is made. The air loss from the control (service) line will eventually activate the tractor protection system which in turn will exhaust the trailer supply (emergency) line and cause the trailer relay emergency valve to apply the trailer brakes.

Front 170

If the foot valve and the hand valve are operated at the same time, can the application air pressure be greater than the reservoir air pressure?

Back 170

no

Front 171

Why is a trailer equipped with spring parking brakes?

Back 171

Spring parking brakes serve as a means of securing a parked trailer whether it is attached to a tractor or not. The spring parking brakes are applied with spring pressure and not air pressure, so there is no risk of the parking brakes releasing and the trailer moving.

Front 172

What brake components are on a trailer equipped with spring parking brakes?

Back 172

• front and rear service reservoirs
• trailer spring brake valve
• relay valve (the same as on a
tractor—not an emergency relay valve used on trailers without spring parking brakes)
• spring parking brake chambers (same as on a tractor)

Front 173

What are the four functions of the trailer spring brake valve?

Back 173

1. It controls the application and release of the trailer’s spring brakes.
2. It protects and isolates the front service reservoir from the rear service reservoir. This is important as it prevents an automatic application of the trailer spring brakes if one of the reservoirs were to lose air pressure.
3. It prevents automatic spring brake application if the trailer supply line has a gradual leak.
4. It will automatically apply the spring parking brakes if supply pressure is rapidly lost (ie: trailer breakaway).

Front 174

"Glad hands" refers to the coupling device used to connect the ________ and ________ lines of the trailer to the tractor.

Back 174

control; supply

Front 175

Before glad hand connection is made, couplers should be ___________.

Back 175

clean

Front 176

________ couplers should be used whenever vehicle is driven without a trailer. Why?

Back 176

"Dead-end"; prevent water and dirt from entering coupler lines

Front 177

The application line is referred to as a _______ (______) line. This line is connected to?

Back 177

control (service); the foot and hand valve

Front 178

Two uses of the trailer brake hand control valve:

Back 178

1. independent control of air to the trailer brake system
2. method of applying the trailer brakes when coupling tractor to trailer

Front 179

The trailer brake hand valve is not to be used for ________. Why? (2 reasons)

Back 179

parking; air might bleed off if the engine is stopped or hand valve may move to released position

Front 180

A two-way check valve will permit air to flow from which source?

Back 180

the source that is supplying the higher application pressure

Front 181

Where is the two-way check valve located?

Back 181

between the foot-operated valve and the hand-operated valve

Front 182

Although the trailer brakes may be applied independently by means of the hand valve, the maximum application pressure can only be ___________.

Back 182

same as, or slightly less than, reservoir pressure.

Front 183

What are the two types of trailer control valves?

Back 183

automatic and manual

Front 184

The trailer supply valve should only be open when the tractor pressure has built up to approximately ____ psi, depending on the valve.

Back 184

90

Front 185

The tractor protection system consists of 2 valves: the _______ valve and the ________ valve.

Back 185

tractor protection valve; trailer supply valve

Front 186

When air lines from the tractor are coupled to a trailer, the opening or closing of the trailer supply valve opens or closes the ___________.

Back 186

tractor protection valve

Front 187

The trailer supply valve should only be open when ____________.

Back 187

the tractor pressure has built up to approximately 90 psi

Front 188

Trailer brakes must not be used to ___________. Why? Therefore, always set the ___________.

Back 188

hold a parked vehicle that is left unattended; loss of pressure will result in loss of brakes; parking brake

Front 189

An older type "manual trailer supply valve" has two positions; ________ and _______.

Back 189

normal; emergency

Front 190

What is the big difference with an older style manual trailer supply valve?

Back 190

In the event of tractor reservoir air loss, the trailer supply valve must be shifted to the emergency position manually to seal off the tractor.

Front 191

Parked trailers without _________ should always have the wheels blocked to prevent a possible runaway.

Back 191

spring parking brakes

Front 192

Parked trailers without spring parking brakes should always __________ to prevent a possible runaway.

Back 192

have the wheels blocked

Front 193

To move a trailer that has been parked with the brakes in an emergency application, it is necessary to _________ to release the trailer brakes.

Back 193

charge the system

Front 194

What is the basic principle of the dual air brake system?

Back 194

Two separate and independent air brakes systems in one with more reservoir capacity.

Front 195

What valve is used to protect the primary circuit from the secondary circuit?

Back 195

one-way check valve

Front 196

In a dual air brake system, will the vehicle continue to have braking ability if one circuit fails?

Back 196

yes

Front 197

Is there a difference between the foot valve used in a basic air brake system and the foot valve used in the dual air brake system?

Back 197

yes, it is really two foot valves in one - one section controls primary reservoir and other section controls secondary reservoir

Front 198

Name two functions of the spring parking brakes in a dual air brake system.

Back 198

1. a parking brake
2. as an emergency braking operation

Front 199

Describe the functions of the spring brake modulator valve.

Back 199

Applies spring brakes if there is a failure in one of the circuits (dual air brake system) and a brake application is made.

Front 200

If the trailer breaks away from the tractor on a dual air brake system, what applies the brakes on the trailer?

Back 200

x

Front 201

What is blended air?

Back 201

x

Front 202

Can a trailer with a basic air brake system be towed by a tractor with a dual air brake system?

Back 202

x

Front 203

What is the purpose of the anti–lock brake system?

Back 203

An anti–lock brake system is an electronic system that monitors wheel speed at all times and controls wheel speed while braking.

Front 204

What three components does an anti–lock brake system consist of?

Back 204

• An electronic control unit (ECU)
• A wheel sensor and tooth wheel
• ABS valves

Front 205

The brain of an anti-lock brake system is the _________.

Back 205

electronic control unit (ECU)

Front 206

How should you apply the brakes when braking on wet or icy roads in a vehicle equipped with anti–lock brakes?

Back 206

brake normally - no pumping

Front 207

Can a trailer with anti–lock brakes be connected to a tractor without anti–lock brake system?

Back 207

yes

Front 208

What is the purpose of the automatic traction control system?

Back 208

monitors wheel spin on acceleration and uses controlled braking to gain traction

Front 209

What two functions does the system use to control traction?

Back 209

differential braking and electronic engine control.

Front 210

ATC is an option only available on vehicles _____________.

Back 210

equipped with ABS

Front 211

Differential braking is activated when the system detects a wheel slipping because ____________.

Back 211

the wheels are operating on different surfaces such as one wheel on dry pavement and the other on ice

Front 212

Electronic engine control is activated automatically by the ATC if __________.

Back 212

all the wheels begin to slip

Front 213

With electronic engine control, engine power is ________ to attain optimum tire–to–road traction without ________.

Back 213

reduced; driver intervention

Front 214

______________ should not be used on slippery surfaces.

Back 214

cruise control

Front 215

Manufacturers recommend that automatic slack adjusters be checked by a mechanic at each _________, or from _______ to _________ km.

Back 215

chassis lubrication interval; 40,000; 80,000

Front 216

What items should you carry to measure and adjust slack adjusters? (4)

Back 216

• A wrench
• A marker to measure pushrod travel
• Sturdy clothing suitable for crawling under the vehicle
• A flashlight

Front 217

When checking brake adjustment, be sure that the vehicle is _________ with the wheels ________.

Back 217

safely parked; wheels blocked.

Front 218

When checking brake adjustment, the air system should be at ________and the _________ released.

Back 218

full pressure; spring parking brakes

Front 219

Two methods for checking the correct brake adjustment:

Back 219

1. Pry method of free stroke measurement
2. Applied stoke method

Front 220

The correct direction to turn the adjusting bolt is _____________.

Back 220

either clockwise or counter-clockwise

Front 221

The push rod and the slack adjuster arm should never ____________ while turning the adjusting bolt.

Back 221

move away from the brake chamber

Front 222

Pushrod strokes with automatic slack adjusters are usually _____________than with well–adjusted manual slack adjusters.

Back 222

slightly longer

Front 223

With a typical Type 30 standard stroke brakechamber, you must adjust the brakes if pushrod measurements are:
1. ________ using the pry method of free stroke measurement,
2. ________ using the brake application—applied stroke method

Back 223

more than 3/4 of an inch; more than 2 inches

Front 224

If you make an emergency adjustment of an automatic slack adjuster, be sure to __________.

Back 224

record it on your daily post–trip inspection report

Front 225

It is strongly recommended that you obtain the _________ for the make of automatic slack adjusters that you are using.

Back 225

service data books

Front 226

Things to check when stopping before a steep hill (6):

Back 226

1. the compressor is maintaining full reservoir air pressure;
2. push rod travel is within limitations on all chambers;
3. there are no air leaks;
4. the glad hands and the lines are secure;
5. the drums, bearings and tires are not overheating;
6. the trailer supply valve is operating properly.

Front 227

The driver must be aware of the condition of the vehicle’s braking system at all times. This can be done by: (3)

Back 227

• watching the pressure gauges
• hearing the warning signals
• feeling the braking response of the vehicle

Front 228

How do you know you are turning the adjusting bolt in the correct direction when adjusting a slack adjuster?

Back 228

the cam will rotate in the same direction that it would if the brakes were being applied

Front 229

What is the first thing you should do when preparing to measure slack adjustment?

Back 229

Be sure that the vehicle is safely parked with the wheels blocked.

Front 230

How much pressure should you apply to the foot valve when measuring slack adjustment using the applied stroke method?

Back 230

between 90 and 100psi

Front 231

What is an advantage of automatic slack adjusters?

Back 231

They don't need manual adjusting - still need to be checked.

Front 232

A person who carries out a vehicle pre–trip inspection must make a trip inspection report in legible writing that contains the following: (5)

Back 232

1. The license plate number or unit number of the vehicle and any trailer towed by it.
2. The date of inspection.
3. A list of any safety defects.
4. If no items are defective or required to be reported on the vehicle or any trailer towed by it, a statement to that effect.
5. The name and signature of the person who carried out the inspection.

Front 233

Every commercial vehicle driver must have a __________ in their possession for the vehicle.

Back 233

current trip inspection report

Front 234

What is the final brake test that should be made before the vehicle is put into service?

Back 234

either the spring parking break - or a final service brake application (not sure)