CDL Air Brakes Test

This is the Commercial Vehicle Driver's License Test covering Air Brakes. You will be presented with 40 questions and you must answer 34 questions correctly to pass. There is no time limit. You may not go back once you answer a question. Click the "Start Quiz" button below to begin. Good luck!

1 / 40

Alcohol evaporators in some air brake systems help to:

cleans out oil from the air lines

it removes fule from the air lines

decreases the risk of water in the air brake valves in cold weather

decrease the chances of ice in the air brake valves in cold weather

2 / 40

You should_____when the low pressure warning is activated:

wait until the air brakes kick in automatically

maintain highway speed and keep an eye on your air pressure gauge

pump the brake pedal to come to a stop immediately

come to a safe stop while you still have control of the brakes

3 / 40

Air pressure should build___with a dual air system.

from 85 to 100 psi in 45 seconds

from 70 to 125 psi in 60 seconds

from 60 to 100 psi in 45 seconds

from 50 to 80 psi in 60 seconds

4 / 40

What is the benefit of ABS?

it provides an added layer of safety for truck drivers

it decreases your stopping distance

it prevents the wheels from locking up during heavy braking or slippery conditions

all of these answers are correct

5 / 40

You should be in the proper gear before going down a hill because:

water may build up in the air tanks if you do not rely on the engine brake

it builds up the air pressure in the air tanks

it helps control your speed better

brakes may fail or fade from excessive heat due to relying on them too much and not using the engine brake effect

6 / 40

What does it man when the safety valve releases air?

you need it to have it checked out by a mechanic because something is wrong

pressure has passed 150 psi

there is too much air in the air compressor

all of these answers are correct

7 / 40

A leak rate for a straight truck or bus air brake system should not exceed _____psi per minute when the engine is off and the brakes are released.

8 / 40

Select what you should do before leaving the vehicle unattended:

chock the wheels

all of these answers are correct

apply the parking brakes

remove the keys from the ignition

9 / 40

Select the true statement in regards to an application pressure gauge:

it shows how much air pressure you are applying to the brakes

it prevents the brakes from failing

it is connected to the generator

when accelerating it releases air

10 / 40

Should your air compressor stop working:

you will lose your ability to brake immediately

there will be no affect to your brakes

the brakes will lock up on you immediately

there will still be air pressure left in the air tanks

11 / 40

When does stab braking occur?

all of these answers are correct

when the wheels start rolling, apply the brakes

apply pressure all the way on the brake pedal

when the wheels lock up, release the brakes

12 / 40

Select the reason as to why air tanks need to be drained:

to realease water and other contaminents which may cause brakes to fail in freezing weather

to prevent the left sided brake from locking up

to provide greater control of your vehicle

tanks usually do not need to be drained

13 / 40

Should the air pressure in the service air tanks fall below____the driver must be alerted via warning mechanism in the truck cab.

60 psi

50 psi

30 psi

80 psi

14 / 40

The safety valve is usually set to open at:

125 psi

150 psi

225 psi

75 psi

15 / 40

You should___to reduce the air leakage rate.

release the service brake as the engine is running

release the service brake after turning off the engine

leave the engine running while charging the air system

monitor the air pressure gauge as you press on the brake pedal

16 / 40

What are spring brakes?

they are powerful springs that are restrained by air pressure when the air pressure is removed, the brakes are applied

they are big springs with air pressure in them if the air pressure decreases, the brakes are applied

none of the answers listed

they are large springs that are held closed by air pressure if the air pressure is increased the brakes are applied

17 / 40

Why do air brakes take longer to stop than hydraulic brakes?

longer reaction time

it takes more time for the air to flow throught the lines

the lines are hotter

none of the answers listed

18 / 40

Select the true statement about tractor protection valve:

it provides the air supply to the brake system

if the air supply drops to a certain level it will automatically close itself

it is closed by the parking brakes

all of these answers are correct

19 / 40

What is the brake system that applies and releases the brakes when the brake pedal is used?

lock brake system

service brake system

none of the answers listed

engine brake system

20 / 40

You should___when driving down a long steep hill.

release the brake once the vehicle is traveling 5 mph below the safe speed

repeatedly pump the brake pedal

use the engine brakes only

begin braking once the vehicle is 10 mph above safe speed

21 / 40

Select the true statement in regards to brake drums or discs:

they are not allowed to have any cracks

the linings should fit loosely around the brake shoe

they should not have cracks that are longer than half the width of the friction area

they should always be kept well-greased up

22 / 40

Water is drained from the compressed air tanks because:

the water will over cool the compressor

to keep the oil in the air compressor clean

braking power is decreased due to the low boiling point of water

the water could freeze in cold weather and cause braking failure

23 / 40

What keeps air in the tanks should the air compressor develop a leak?

the one-way check vavle

the air compressor

the tractor relay valve

the engine protection valve

24 / 40

Select the purpose of fanning air brakes:

it increases the air pressure

it decreases the braking power

lower air pressure

it cools them down

25 / 40

The parking brakes should be used____in air brake vehicles.

only when parked on an incline

every time the vehicle is parked

as rarely as possible

only during post trip inspection

26 / 40

How do you test your service brakes?

after releasing the parking brake, move forward slowly and apply pressure to the brake pedal

release the air pressure and activate the parking brake

apply pressure to the brake pedal when moving at highway speeds

pull over and activate the parking brake

27 / 40

Select whether the following statement is true or false: Front wheel brakes are good to use in all conditions.

only in ideal conditions

only in bad weather

true

false

28 / 40

Is it mandatory that all vehicles with air brakes have low air pressure warning signals?

for small vehicles only

for large vehicles only

yes

29 / 40

Air pressure loss in a vehicle with a fully charged air system should be less than_______after the initial drop and brake applied.

1 psi a minute

none of the answers listed

4 psi a minute

3 psi a minute

30 / 40

What is a supply pressure gauge used for?

it tells you how much pressure is in the air tanks

all of these answers are correct

it tells you how much slack is in the slack adjusters

it tells you how much pressure is in the air lines

31 / 40

How do you know when your brakes are fading?

to control your speed on a downgrade you have to push harder on the brake pedal

the brake pedal flops to the cabin floor

to control your speed on a downgrade you have to apply less pressure to the break pedal

your speed increases when pressure is removed from the brake pedal

32 / 40

You should____to check the free play of manual slack adjusters on S-Cam brakes.

after parking on a slight grade, release the parking brake, activate the service brakes and check for vehicle movements

chock the wheels and release the parking brakes after parking on a level ground

drain off air pressure before adjusting after parking on level ground

apply the parking brake after stopping on level ground

33 / 40

Select the true statement about dual air brake systems:

they have a single set of air tanks and hoses

they have one set of controls for two air brake systems

they are required to have two warning alarms

they require less time to build up air pressure

34 / 40

What does the air compressor governor control?

when air pressure is applied to the brakes

when the vavle system releases pressure

when air is pumped into the air tanks

when the air is taken out of the hoses

35 / 40

Spring brakes are usually held back by_____during normal driving.

pressure of the spring

air pressure

clamps

heat

36 / 40

What are slack adjusters?

all of these answers are correct

they are between the push rod on disc brakes and power screw

they are between the S-Cam on drum brakes and the push rod

they are a part of the air brake system that adjusts the brakes

37 / 40

How often should you drain your air tanks?

at the end of each week

at the beginning of each month

at the end of each trip

at the end of each shift

38 / 40

Select the statement that tells you how you can check the low pressure warning signal.

Turn the electrical power off and apply pressure on and off the brake pedal to decrease air tank pressure. The low air pressure warning signal must come on before the pressure drops to less than 30 psi in the air tank.

The low pressure warning signal is only testable by the factory.

Turn the electrical power on and apply pressure on and off the brake pedal to decrease the air tank pressure. The low air pressure warning signal must come on before the pressure drops to less than 60 psi in the air tank.

Turn the electrical power on and apply pressure on and off the brake pedal to increase air tank pressure. The low air pressure warning signal must come on before the pressure increases to more than 60 psi in the air tank.

39 / 40

Air brake systems should not lose air faster than____when testing for air leakage rates in combination vehicles before applying the brake pedal.

3 psi a minute

2 psi a minute

5 psi a minute

6 psi a minute

40 / 40

The 3 parts of the air brake system are: service brakes, parking brakes, and ____.

v-cam brakes

bolt brakes

disc brakes

foot brakes

Your score is

The average score is 74%

5/5 - (1 vote)

CDL Air Brakes Test

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