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

Select the true statement in regards to the braking power of spring brakes.

the braking prower increases when the brakes are hot

it depends on the adjustment of the service brakes

braking power can only be tested by licensed mechanics

it will not be affect by the condition of the service brakes

2 / 40

What does it man when the safety valve releases air?

pressure has passed 150 psi

all of these answers are correct

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

there is too much air in the air compressor

3 / 40

Air tanks need to be drained:

to prevent water and oil from building up in the tank

to keep the tanks warm when not in use

to keep the tanks cold when not in use

air tanks should absolutely never be drained

4 / 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

apply the parking brake after stopping on level ground

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

5 / 40

What does the air compressor governor control?

when the vavle system releases pressure

when air is pumped into the air tanks

when air pressure is applied to the brakes

when the air is taken out of the hoses

6 / 40

What are slack adjusters?

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

all of these answers are correct

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

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

7 / 40

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

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

pull on the slack adjuster while the parking brakes are on

8 / 40

What does the drain valve for air tanks remove?

oil and water

air and oil

oil and dirt

water and air

9 / 40

Select how you would check the truck's slack adjusters.

all of these answers are correct

while wearing gloves, pull hard on each slack adjuster that you can reach

brake hard after accelerating

listen for any strange noises while applying pressure to the brake pedal

10 / 40

Select the purpose of fanning air brakes:

it decreases the braking power

lower air pressure

it cools them down

it increases the air pressure

11 / 40

Select the answer that is not a part of the braking process when driving a tractor-trailer combination vehicle that has ABS:

only use the braking that is necessary to safely stay in control of the vehicle

you should drive at a higher speed to keep the trailer in line

you should monitor the tractor and trailer as you decrease your speed to keep control

you should brake in the same manner regardless of what you are driving

12 / 40

How often should you drain your air tanks?

at the end of each trip

at the end of each shift

at the beginning of each month

at the end of each week

13 / 40

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

engine brake system

none of the answers listed

service brake system

lock brake system

14 / 40

Select what you should do before leaving the vehicle unattended:

all of these answers are correct

remove the keys from the ignition

apply the parking brakes

chock the wheels

15 / 40

____is what can legally hold the parking brake or emergency brake in position for a bus, truck, or truck tractor.

brake pressure

spring pressure

air pressure

all of these answers are correct

16 / 40

Why are you required to take an exam about air brakes?

you would have to get a CDL with a restriction otherwise

all trucks have air brakes

you cannot receive a CDL at all otherwise

it is a federal requirement

17 / 40

Where is compressed air stored?

in the hose lines

in the gasoline tank

in the storage tank

in the compartment for the engine

18 / 40

When should you avoid using the parking brake?

whenever you park

when the brakes are hot

when the air pressure is low

while on an incline

19 / 40

Select the true statement about tractor protection valve:

all of these answers are correct

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

it is closed by the parking brakes

it provides the air supply to the brake system

20 / 40

Select the true statement about slack adjusters:

they should move a minimum of 2 inches from the push rod attachment

they do not ever need to be adjsuted

they should only be adjusted by a mechanic that is certified in slack adjusters

they can be adjusted automatically or manually

21 / 40

How do you test your service brakes?

apply pressure to the brake pedal when moving at highway speeds

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

pull over and activate the parking brake

release the air pressure and activate the parking brake

22 / 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)

when using the engine brake more than the brakes

excessive heat from extensive use

tire retread that is mismatched

brakes that are not aligned properly

23 / 40

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

80 psi

30 psi

60 psi

50 psi

24 / 40

Select which vehicles are required to have a low air pressure warning signal:

all vehicles built after 2005

all operating vehicles with air brakes

all vehicles built after 2010

they are optional

25 / 40

How often should air tanks be drained?

every 7 days

every 4-5 days

every 6 hours

once a day

26 / 40

The best way to describe a dual air brake system is:

there are 2 separate air brake systems that have their own hoses, lines etc

there is a primary and secondary system that is 2 separate air brake systems

there are 2 separate air brake systems that supply air to the trailer if there is one

all of these answers are correct

27 / 40

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

3 psi a minute

4 psi a minute

1 psi a minute

none of the answers listed

28 / 40

When should you not use the parking brakes?

when the brakes are hot

while in hot weather

when air pressure is low

while on a steep hill

29 / 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

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

continue on with your trip

30 / 40

When does stab braking occur?

when the wheels lock up, release the brakes

apply pressure all the way on the brake pedal

all of these answers are correct

when the wheels start rolling, apply the brakes

31 / 40

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

brake drum

axle

safety valve

slack adjuster

32 / 40

How do you know when your brakes are fading?

your speed increases when pressure is removed from the brake pedal

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

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

the brake pedal flops to the cabin floor

33 / 40

Select how brakes work on long, steep downgrades:

they are a supplement to the braking effect of the engine

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

it does not do anything

it is the main braking mechanism

34 / 40

The best way to test if the spring brakes come on automatically is to:

apply pressure on and off the brake pedal until the parking valve pops out on single vehicles

apply pressure on and off the brake pedal until the parkng brake valve pops out on tractor-trailer vehicles

all of these answers are correct

apply pressure on and off the brake pedal until the manufacturer's low psi specification has been met for the spring brakes to deploy

35 / 40

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

monitor the air pressure gauge

decrease the tank pressure by stepping on and off the brake

all of these answers are correct

run the engine at a fast idle

36 / 40

Water is drained from the compressed air tanks because:

the water will over cool the compressor

the water could freeze in cold weather and cause braking failure

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

to keep the oil in the air compressor clean

37 / 40

The parking brakes should be used____in air brake vehicles.

every time the vehicle is parked

only during post trip inspection

as rarely as possible

only when parked on an incline

38 / 40

The safety valve is usually set to open at:

75 psi

125 psi

150 psi

225 psi

39 / 40

____is the most common type of foundation brakes used by heavy vehicles.

none of the answers listed

rectangle brakes

wedge drum

S-Cam drum

40 / 40

Select the true statement in regards to brake drums:

they are located at both ends of the axles of the vehicle

they are bolted to the wheels

all of these answers are correct

hold the brake linings and shoes

Your score is

The average score is 84%

5/5 - (1 vote)

CDL Air Brakes Test

CDL Category Practice Tests