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

What are slack adjusters?

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

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

2 / 40

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

225 psi

150 psi

125 psi

100 psi

3 / 40

The safety valve is usually set to open at:

125 psi

225 psi

150 psi

75 psi

4 / 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 full hand valve until you stop and press firmly on the brake pedal

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

rapidly and lightly pump the brake pedal

5 / 40

How often should you drain your air tanks?

at the end of each trip

at the beginning of each month

at the end of each shift

at the end of each week

6 / 40

You should___when driving down a long steep hill.

begin braking once the vehicle is 10 mph above safe speed

use the engine brakes only

repeatedly pump the brake pedal

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

7 / 40

Select the true statement about dual air brake systems:

they require less time to build up air pressure

they have a single set of air tanks and hoses

they are required to have two warning alarms

they have one set of controls for two air brake systems

8 / 40

What does the service brake system do?

they are valves that maintain air tank pressure

they are only on vehicles that have hydraulic brakes

under normal driving it applies and releases the brakes by using the brake pedal

they are part of an official vehicle inspection

9 / 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

60 psi

30 psi

50 psi

10 / 40

At what "cut out" level does the governor stop pumping air?

75 psi

125 psi

100 psi

150 psi

11 / 40

Air pressure should build___with a dual air system.

from 50 to 80 psi in 60 seconds

from 70 to 125 psi in 60 seconds

from 85 to 100 psi in 45 seconds

from 60 to 100 psi in 45 seconds

12 / 40

When should air tanks be drained?

at the end of each working day

they don't need to be drained

at every restroom break stop

every 7 days

13 / 40

What is the benefit of ABS?

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

it provides an added layer of safety for truck drivers

all of these answers are correct

it decreases your stopping distance

14 / 40

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

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

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

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

15 / 40

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

they are optional

all operating vehicles with air brakes

all vehicles built after 2005

all vehicles built after 2010

16 / 40

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

4 psi a minute

3 psi a minute

1 psi a minute

none of the answers listed

17 / 40

Select the true statement about slack adjusters:

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

they can be adjusted automatically or manually

they do not ever need to be adjsuted

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

18 / 40

Is this statement true or false: you do not need to use the parking brake if are leaving your vehicle for a short amount of time.

only when the vehicle has over 60,000 miles on it

only when the vehicle has over 25,000 miles on it

true

false

19 / 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 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.

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.

20 / 40

Where is compressed air stored?

in the gasoline tank

in the hose lines

in the storage tank

in the compartment for the engine

21 / 40

Select the true statement about tractor protection valve:

all of these answers are correct

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

22 / 40

Front wheel brakes are good under what kind of conditions?

they are not ideal

icy or wet conditions

ideal weather conditions

any weather conditons

23 / 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

brakes that are not aligned properly

tire retread that is mismatched

24 / 40

Should your air compressor stop working:

there will still be air pressure left in the air tanks

you will lose your ability to brake immediately

the brakes will lock up on you immediately

there will be no affect to your brakes

25 / 40

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

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

braking power can only be tested by licensed mechanics

the braking prower increases when the brakes are hot

it depends on the adjustment of the service brakes

26 / 40

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

only in bad weather

true

only in ideal conditions

false

27 / 40

What does the drain valve for air tanks remove?

oil and water

water and air

air and oil

oil and dirt

28 / 40

Select the true statement in regards to brake drums:

hold the brake linings and shoes

they are bolted to the wheels

all of these answers are correct

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

29 / 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

30 / 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.

31 / 40

How often should air tanks be drained?

once a day

every 6 hours

every 4-5 days

every 7 days

32 / 40

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

axle

safety valve

slack adjuster

brake drum

33 / 40

How do you know when your brakes are fading?

the brake pedal flops to the cabin floor

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

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

34 / 40

Water is drained from the compressed air tanks because:

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

the water could freeze in cold weather and cause braking failure

the water will over cool the compressor

to keep the oil in the air compressor clean

35 / 40

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

when the vehicle is runaway

yes

when the GVCW is above 20,000 lbs

36 / 40

Select the true statement about what the Air Compressor Governor controls:

it controls when the air compressor pumps air into the storage tanks

it controls when the warning system is activated

it controls when the brakes will be applied

it controls when air is released from the storage tank

37 / 40

When should you not use the parking brakes?

while on a steep hill

when air pressure is low

when the brakes are hot

while in hot weather

38 / 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

39 / 40

The compressor is connected to the engine via _____?

lines

v-belt or gears

stag gears

r-belt

40 / 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

Your score is

The average score is 82%

5/5 - (1 vote)

CDL Air Brakes Test

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