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

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

150 psi

75 psi

100 psi

125 psi

2 / 40

Select the true statement about slack adjusters:

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

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

they do not ever need to be adjsuted

they can be adjusted automatically or manually

3 / 40

An air system that is fully charged will typically have ___ psi of pressure.

200

250

125

4 / 40

The compressor is connected to the engine via _____?

r-belt

stag gears

lines

v-belt or gears

5 / 40

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

for small vehicles only

yes

for large vehicles only

6 / 40

What is a supply pressure gauge used for?

it tells you how much pressure is in the air lines

all of these answers are correct

it tells you how much pressure is in the air tanks

it tells you how much slack is in the slack adjusters

7 / 40

How do you know when your brakes are fading?

your speed increases when pressure is removed from 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

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

8 / 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 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

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

9 / 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.

10 / 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

11 / 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

rapidly and lightly pump 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

12 / 40

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

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

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

it helps control your speed better

it builds up the air pressure in the air tanks

13 / 40

Air pressure should build___with a dual air system.

from 85 to 100 psi in 45 seconds

from 60 to 100 psi in 45 seconds

from 50 to 80 psi in 60 seconds

from 70 to 125 psi in 60 seconds

14 / 40

Commerical vehicles typically have this type of brake.

drum brakes

S-Cam brakes

stab brakes

rectangle brakes

15 / 40

With the engine cutt off and the brakes released the air loss in a straight truck or bus should not be more than:

4 psi in a minute

2 psi in a minute

3 psi in a minute

5 psi in a minute

16 / 40

Air tanks should be drained:

at the end of each shift or day

all of these answers are correct

to prevent sludge from clogginng up the brake system valves

manually when the automatic devices fail

17 / 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

they are part of an official vehicle inspection

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

18 / 40

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

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

apply the parking brake after stopping on level ground

drain off air pressure before adjusting after parking on level ground

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

19 / 40

How can you check slack adjusters?

it is not possible to check manually

by using a fixed wrench

by frequenctly checking the pressure gauge

by pulling hard on each slack adjuster

20 / 40

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

tanks usually do not need to be drained

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

to provide greater control of your vehicle

to prevent the left sided brake from locking up

21 / 40

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

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

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

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

all of these answers are correct

22 / 40

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

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

pull hard on each slack adjuster while wearing gloves

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

pull on the slack adjuster while the parking brakes are on

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

50 psi

30 psi

60 psi

24 / 40

Air tanks need to be drained:

air tanks should absolutely never be drained

to keep the tanks cold when not in use

to keep the tanks warm when not in use

to prevent water and oil from building up in the tank

25 / 40

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

they should always be kept well-greased up

they are not allowed to have any cracks

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

the linings should fit loosely around the brake shoe

26 / 40

Where is compressed air stored?

in the hose lines

in the storage tank

in the gasoline tank

in the compartment for the engine

27 / 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

28 / 40

Select when you should use the parking brake:

each time you leave your vehicle for any amount of time

when in residential areas

with rare exception, every time you leave your vehicle

when you are leaving your vehicle for more than an hour

29 / 40

Alcohol evaporators in some air brake systems help to:

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

cleans out oil from the air lines

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

it removes fule from the air lines

30 / 40

Select the statement that is not part of the air-brake system:

emergency brake system

clutch brake system

parking brake system

service brake system

31 / 40

How often should you drain your air tanks?

at the end of each week

at the end of each shift

at the end of each trip

at the beginning of each month

32 / 40

How do you test your service brakes?

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

apply pressure to the brake pedal when moving at highway speeds

33 / 40

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

activiate the parking brake and service brake

release the parking brakes and service brakes

pull out the automatic slack adjustment control knob

release the parking brakes and activate the service brakes

34 / 40

What must vehicles with air brakes have?

a minimum of 2 air tanks

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

all of these answers are correct

an air pressure gauge that shows the pressure available for braking

35 / 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

36 / 40

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

all of these answers are correct

brake hard after accelerating

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

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

37 / 40

The method used to make sure the spring brakes will come on automatically is to:

Apply pressure on and off the brake pedal to decrease the air tank pressure. The parking brake knob should pop out when the air pressure meets to the manufacturer’s specification.

Apply pressure on and off the brake pedal to decrease the air tank pressure while driving at a high a speed. The parking brake knob should pop out when the air pressure meets to the manufacturer’s specification.

Apply pressure on and off the brake pedal to decrease the air tank pressure. The parking brake knob should pop out when the air pressure drops to 120 psi.

Apply pressure on and off the brake pedal to increase the air tank pressure. The parking brake knob should pop out when the air pressure meets to the manufacturer’s specification.

38 / 40

An example of a low pressure warning signal for air brakes is:

all of these answers are correct

red light

a wig wag mechanical arm

a buzzer

39 / 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

40 / 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 manufacturer's low psi specification has been met for the spring brakes to deploy

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

Your score is

The average score is 82%

5/5 - (1 vote)

CDL Air Brakes Test

CDL Category Practice Tests