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Louisiana CDL DMV Air Brakes 2

Take 6 practice tests for CDL is the best way to prepare for your Louisiana DMV exam is by taking our free practice tests. The following question are from real Louisiana DMV practice test. More than 95% people pass a DMV exam when practice at DMV Practice Test.

Number of Test
6
Number of Question
25
Passing score
20
13%
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  • 0Incorrect
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1. Manual air tank drains should be:
Opened to drain the tanks after each day.
Left open while driving.
Sealed with glue.

Compressed air in an air brake system usually contains a certain amount of water and compressor oil. The water and oil can damage the brakes if left to accumulate in the system. Manually operated air tank drains must be opened daily to remove this build-up.

2. When stopping in an emergency situation, you should:
Veer your trailer to the right and stop.
Stop in a straight line.
Veer your trailer to the left and stop.

If you need to make an emergency stop, you can use either the controlled braking method or the stab braking method. It's important to brake in a way that keeps your vehicle in a straight line but will still allow you to turn if necessary.

3. Brakes out of adjustment will:
Work properly.
Cause some of the brakes to overwork and malfunction.
Allow better acceleration.

Brakes out of adjustment will fade before those that are properly adjusted. Brake adjustment must be checked frequently to help prevent brake issues.

4. Do not operate a vehicle if any brake drums have cracks that are larger than ____ of the width of the friction area.
One half
One third
One fifth

Before beginning a trip, it is important to check the brake drums during your walk-around inspection. It is unsafe to drive if any brake drum has a crack more than one half of the width of the friction area.

5. An air compressor governor controls:
When the air compressor pumps air into the air storage tanks.
How fast air is pumped into the air storage tanks.
The temperature of the air pumped into the air storage tanks.

In an air brake system, the air compressor governor controls when the air compressor pumps air into the air storage tanks.

6. If the low air pressure warning signal comes on, you should:
Continue driving, but have the brakes repaired within a week.
Pull over and inspect the brakes.
Phone a mechanic while driving.

If the low air pressure warning signal comes on while you are driving a vehicle with air brakes, you should immediately bring the vehicle to a safe stop while you are still able to control the brakes. Inspect and repair the brakes as soon as possible.

7. The air storage tanks:
Hold only enough air for one braking cycle.
Hold enough air for the brakes to be used several times if the compressor stops working.
Do not hold air unless there is an emergency.

The air storage tanks in an air brake system store compressed air to be used for braking. They hold enough air for the brakes to still be used several times if the compressor stops working.

8. Braking mechanisms are located inside:
The fifth wheel.
A brake drum.
The landing gear.

Drum brakes are attached to the wheels and located on the axles of a vehicle. The braking mechanisms that cause the vehicle to stop can be found inside of a drum brake.

9. What does the air compressor governor do?
It stops the compressor from pumping air.
It turns on the air compressor.
It stores the compressed air.

In an air brake system, the air compressor governor controls when the air compressor pumps air into the storage tanks. It stops pumping if the pressure in the tanks becomes too high, and begins pumping if the pressure becomes too low.

10. Using an Anti-Lock Braking System (ABS):
Is required in some states.
Shortens brake response time.
Provides additional control.

An Anti-Lock Braking System (ABS) helps to provide additional control during hard braking, but does not necessarily shorten a vehicle's stopping distance.

11. What do air brakes use to make the brakes work?
Compressed air
Outside air
Non-compressed air

Many large CMVs are equipped with air brakes. An air braking system uses compressed air to operate.

12. What is removed when an air tank is drained?
Water and oil
Ammonia
Liquid cleaners

In an air brake system, air tanks have drains to remove accumulations of water and compressor oil. Allowing water and oil to accumulate in the system could cause damage to the brakes.

13. When leaving your vehicle unattended:
The parking brake must be always be used.
The parking brake should never be used.
Windows in the cab should be lowered.

Always apply the parking brake when leaving your vehicle unattended.

14. A slack adjuster should move no more than ____ from where it is attached to the push rod.
Two inches
Five inches
One inch

Before a trip, you should check each slack adjuster after parking, setting wheel chocks, and disengaging the parking brake. Pull the slack adjusters to make sure that they do not move more than about one inch from where the push rod is attached. If they move more than one inch, they may be out of adjustment and will need to be fixed.

15. What is often found in compressed air?
Water
Cardboard
Brake fluid

Compressed air in an air brake system usually contains a certain amount of water and compressor oil. The water and oil can damage the brakes if left to accumulate in the system. Tanks must be drained regularly to remove this build-up.

16. Why should you regularly drain the air tanks?
Because the air gets old and needs to be replaced
Because compressed air contains some water and the water collects in the tanks
To allow for a change in pressure

Compressed air usually contains a certain amount of moisture and compressor oil, which can build up in the air storage tanks and damage the brake system. The tanks should be drained to clean out these accumulations. On a tank with a manual drain valve, draining should be performed at the end of each day of driving.

17. While driving, ____ generally holds spring brakes in place.
Air pressure
Electricity
Gasoline

While driving, spring brakes are generally held in place by air pressure. If the air pressure gets low enough, the springs will activate the brakes.

18. The ____ between an air compressor and reservoir tank prevents air from escaping if the air compressor has a leak.
Slack adjuster
One-way check valve
Tractor protection valve

A one-way check valve is required to be between an air compressor and the first main reservoir. This valve prevents air from escaping the system if the air compressor develops a leak.

19. Alcohol evaporators are:
Illegal.
Used to add alcohol to braking systems to prevent items from freezing.
Only allowed on vehicles carrying hazardous materials.

Some air brake systems include an alcohol evaporator. The evaporator introduces alcohol into the braking system to prevent the formation of ice, which can cause damage.

20. You should ____ if the low pressure warning signal activates while you are driving.
Stop where you are and park
Exit the roadway as soon as safely possible
Continue driving normally

If the low pressure warning signal activates while you are driving, it is important that you safely exit the roadway as soon as possible and park your vehicle. If the air pressure gets too low, the brakes will no longer work well enough for you to stop safely.

21. An Anti-Lock Braking System (ABS):
Is not available for vehicles with air brakes.
Is not helpful in most driving situations.
Can help you maintain control when braking.

Anti-Lock Braking Systems (ABS) are compatible with air brakes and help a driver maintain control of their vehicle by preventing wheel lockup.

22. A wig wag is:
A low pressure warning device.
A tube that carries air to the brakes.
A type of air brake system.

Vehicles with air brakes are required to be equipped with a low pressure warning device. A wig wag is a type of low air pressure warning device. This device drops a mechanical arm into the driver's view if the pressure in the tanks drops to a level between 55 and 75 psi.

23. When an S-cam turns inside a brake drum, the S-cam:
Presses the brake shoes against the inside of the brake drum.
Presses the brake shoes against the brake linings.
Presses the brake linings against the wheel axles.

When a brake pedal is pressed and the S-cam is turned, the S-cam presses the brake shoes against the inside of the brake drum. This causes friction and will cause the vehicle to slow.

24. What is brake lag?
The time required for the brakes to work after the brake pedal is pressed
The distance between the brake pedal and the floor
The amount of air pressure used to stop the vehicle

Because air takes time to flow through the air lines to the brakes, air brakes cannot begin working instantly. There is often a brake lag of at least one-half of a second between the moment the brake pedal is pressed and the moment the brakes begin to work.

25. What tells you how much pressure is in your vehicle's air tanks?
The supply pressure gauge
The ABS malfunction lamp
The tractor protection valve

A vehicle that is equipped with air brakes must also be equipped with a supply pressure gauge. This gauge tells the driver how much air pressure is in each of the vehicle's air tanks.

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