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

When should air tanks be drained?

they don't need to be drained

every 7 days

at the end of each working day

at every restroom break stop

2 / 40

What is a supply pressure gauge used for?

it tells you how much pressure is in the air lines

it tells you how much pressure is in the air tanks

it tells you how much slack is in the slack adjusters

all of these answers are correct

3 / 40

How do you determine if slack adjusters need to be adjusted?

release the parking brakes and activate the service brakes

release the parking brakes and service brakes

activiate the parking brake and service brake

pull out the automatic slack adjustment control knob

4 / 40

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

for large vehicles only

yes

for small vehicles only

5 / 40

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

drain off air pressure before adjusting after parking on level ground

apply the parking brake after stopping on level ground

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

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

6 / 40

You should_____when the low pressure warning is activated:

wait until the air brakes kick in automatically

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

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

pump the brake pedal to come to a stop immediately

7 / 40

Select the factor that is known to cause brakes to fail or fade. (more than one answer may be correct, but select only one)

brakes that are not aligned properly

when using the engine brake more than the brakes

excessive heat from extensive use

tire retread that is mismatched

8 / 40

When does your vehicle's single brake system need an adjustment?

when the governor stops between 75-90 psi

if the compressor cuts out at between 70 and 90 psi

if the pressure builds from 50 to 75 psi in less than 3 minutes

when the pressure builds from 85 to 100 psi in less than 1 minute

9 / 40

What does the drain valve for air tanks remove?

oil and water

air and oil

water and air

oil and dirt

10 / 40

Select the inappropriate way to test for the low pressure warning signal.

have the electrical power on

ask for a pedestrian to listen for the signal

turn off the engine

decreased the air pressure by stepping on and off the brake pedal

11 / 40

Air pressure should build___with a dual air system.

from 60 to 100 psi in 45 seconds

from 70 to 125 psi in 60 seconds

from 50 to 80 psi in 60 seconds

from 85 to 100 psi in 45 seconds

12 / 40

The compressor is connected to the engine via _____?

lines

stag gears

r-belt

v-belt or gears

13 / 40

Spring brakes are usually held back by_____during normal driving.

air pressure

pressure of the spring

clamps

heat

14 / 40

Select when you should use the parking brake:

when you are leaving your vehicle for more than an hour

each time you leave your vehicle for any amount of time

with rare exception, every time you leave your vehicle

when in residential areas

15 / 40

What are spring brakes?

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

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

16 / 40

What should you do if the low air pressure warning comes on for only one system in a truck or bus that has a dual air brake system?

decrease your speed and head to the closest mechanic

decrease your speed and test the other system

continue on with your trip

stop and safely park your vehicle only continue once the issue has been resovled

17 / 40

You should_____when checking the slack adjusters on S-Cam brakes.

pull on the slack adjuster while the parking brakes are on

pull hard on each slack adjuster while wearing gloves

make sure there is an inch of leeway in each direction for the slack adjuster

pull on the slack adjusters after draining the air form the system

18 / 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

19 / 40

Air tanks should be drained:

to prevent sludge from clogginng up the brake system valves

manually when the automatic devices fail

all of these answers are correct

at the end of each shift or day

20 / 40

At what pressure is the safety valve in the air compressor tank set to open?

150 psi

125 psi

225 psi

100 psi

21 / 40

Select the true statement about tractor protection valve:

it provides the air supply to the brake system

it is closed by the parking brakes

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

all of these answers are correct

22 / 40

You should___to reduce the air leakage rate.

release the service brake as the engine is running

leave the engine running while charging the air system

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

release the service brake after turning off the engine

23 / 40

A slack adjuster is:

a lever that connects the return spring and the brake chamber push rod

a lever that connects the brake chamber push rod with the foundation brake camshaft

a lever that connects the brake drum to the brake shoe

a lever that connects the brake camshaft with the brake chamber

24 / 40

You should brake on a long steep downgrade hill as a supplement to the braking effects of the engine

when the GVCW is above 20,000 lbs

when the vehicle is runaway

yes

25 / 40

You should_____to make an emergency stop with air brakes when using the stab braking method.

apply pressure to the brake pedal until the wheels lock and then stay off of the pedal for as long as the wheels are locked

apply a firm pressure to the brakes, release the brake pedal once the wheels lock and then apply pressure to the brakes onces the wheels start rolling again

apply a full hand valve until you stop and press firmly on the brake pedal

rapidly and lightly pump the brake pedal

26 / 40

How can you check slack adjusters?

by pulling hard on each slack adjuster

by using a fixed wrench

by frequenctly checking the pressure gauge

it is not possible to check manually

27 / 40

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

the one-way check vavle

the tractor relay valve

the engine protection valve

the air compressor

28 / 40

Select the part that is not a part of the drum brake:

slack adjuster

brake drum

safety valve

axle

29 / 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

there is too much air in the air compressor

all of these answers are correct

pressure has passed 150 psi

30 / 40

How do you check the air compressor governor "cut in" and "cut out" pressures?

all of these answers are correct

decrease the tank pressure by stepping on and off the brake

run the engine at a fast idle

monitor the air pressure gauge

31 / 40

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

when accelerating it releases air

it is connected to the generator

it prevents the brakes from failing

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

32 / 40

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

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.

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 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.

33 / 40

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

none of the answers listed

longer reaction time

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

the lines are hotter

34 / 40

Select how brakes work on long, steep downgrades:

it's the main braking mechanism with the engine braking system available for emergency situations

it does not do anything

they are a supplement to the braking effect of the engine

it is the main braking mechanism

35 / 40

The safety valve is usually set to open at:

125 psi

150 psi

75 psi

225 psi

36 / 40

How often should air tanks be drained?

every 7 days

once a day

every 4-5 days

every 6 hours

37 / 40

What must vehicles with air brakes have?

all of these answers are correct

an air pressure gauge that shows the pressure available for braking

an air pressure gauge that shows how much air is used by the brake chambers for braking

a minimum of 2 air tanks

38 / 40

At around____the governor allows the air compressor to start pumping again:

175 pso

225 psi

125 psi

100 psi

39 / 40

Water is drained from the compressed air tanks because:

the water could freeze in cold weather and cause braking failure

the water will over cool the compressor

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

to keep the oil in the air compressor clean

40 / 40

Commerical vehicles typically have this type of brake.

stab brakes

drum brakes

rectangle brakes

S-Cam brakes

Your score is

The average score is 82%

5/5 - (1 vote)

CDL Air Brakes Test

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