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Illinois CDL DMV Air Brakes 2

Take 6 practice tests for CDL is the best way to prepare for your Illinois DMV exam is by taking our free practice tests. The following question are from real Illinois 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. A dual air brake system:
Has a single air brake system, but uses two sets of controls.
Has one air brake system for each side of the truck.
Has two brakes for each wheel.
Has two separate air brake systems, but uses a single set of controls.

A dual air brake system has two separate air brake systems that use a single set of brake controls. One system typically operates the regular brakes on the rear axle or axles. The other system operates the regular brakes on the front axle.

2. On a truck with air brakes, the braking system’s air compressor:
Pumps air into the air storage tanks.
Fills the tires.
Moves air to the back of the truck.
Cleans the brakes.

In an air brake system, the air compressor pumps air into the air storage tanks. The air compressor is controlled by the air compressor governor.

3. Air tank drains:
Allow rain water to enter the tanks.
Are used to drain water and oil from the tanks.
Should never be opened.
Must remain open while driving.

In an air brake system, the air storage tanks are equipped with drains to allow water and compressor oil to be removed. The water and oil can damage the brakes if left to accumulate in the system.

4. When inspecting your brakes, a slack adjuster should move ____ from where it is attached to the push rod.
At least three inches
More than two inches
Up to five inches
No more than one inch

Check each slack adjuster after setting wheel chocks and disengaging the parking brake. Pull the slack adjusters to make sure 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.

5. Most heavy-duty vehicles use:
Single air brake systems.
Dual air brake systems.
Triple air brake systems.
Quadruple air brake systems.

Most heavy-duty vehicles use dual air brake systems, in which there are two separate braking systems operated by a single set of controls. Each system operates the brakes on different axles.

6. During a static leakage test, the maximum leakage rate for a single vehicle with air brakes is ____ in one minute.
1 psi
2 psi
3 psi
4 psi

When performing a static leakage test on a single vehicle with air brakes, the leakage rate should be no more than 2 psi in a minute. If air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.

7. In a dual air brake system, a leak in one system:
Always means there are leaks in both systems.
May not affect the other system.
Is not something to worry about.
Will also affect the other system.

A dual air brake system is made up of two separate air brake systems. If there is an air leak in one system, it may not affect the other.

8. Test the low pressure warning signal:
Once a month.
Once a week.
Twice a week.
Before every trip.

It is essential that your low pressure warning light function properly. After allowing the system to charge, you can test the warning signal by rapidly applying and releasing the brake pedal. This will release air from the braking system and the warning signal should come on when pressure drops to a dangerous level.

9. When about to drive a vehicle with a dual brake system, a driver should:
Let the vehicle warm up to ensure the fuel reaches the engine.
Wait for air pressure to build in both the primary and secondary systems.
Begin driving just after the engine starts.
Pump the pedal about 20 times to build pressure, then begin driving.

Before driving a vehicle with a dual air brake system, allow time for the compressor to build up pressure to at least 100 psi in both systems.

10. In a dual air brake system:
Each system has separate air tanks, hoses, and lines.
The systems share air tanks, but each has its own separate hoses and lines.
Each system uses the same lines and hoses.
One system is the main braking system and a second system is ready to be used if the first one fails.

A dual air brake system is made up of two separate air brake systems. The systems share a single set of brake controls, but each has its own air tanks, hoses, and lines.

11. If you’re driving and the ABS warning light comes on, it means:
The ABS is working properly.
The ABS has just been activated.
The ABS is not working properly.
The ABS needs to be activated.

Vehicles with Anti-Lock Braking Systems (ABS) have yellow malfunction lights to alert the driver if something is wrong with the braking system. If these lights activate, the driver may have lost ABS on one or more wheels.

12. When traveling down a steep downgrade:
The air brakes should be used.
Shift into a lower gear, then use brakes to supplement the braking effect of the engine.
The vehicle should be continually downshifted in the place of using the brakes.
The vehicle should be driven on the shoulder.

On a downgrade, the braking effect of the engine should be your primary method of controlling speed. Shift down to a lower gear before starting down the hill and save the brakes for additional slowing or stopping that may be required by road or traffic conditions.

13. If the spring brakes are on, you should:
Not use the brake pedal.
Press the accelerator.
Move the steering wheel.
Be especially careful because the brakes may fail.

You should not apply the brake pedal if the spring brakes are activated. The brakes could be damaged if they are subjected to the force of air pressure and the springs at the same time.

14. If your tractor is equipped with ABS but your trailer is not, the ABS:
Will not be effective.
Will still improve your steering control.
Will make jackknifing easier.
Will allow others to see when you brake.

In a tractor-trailer combination, if the tractor is equipped with an Anti-Lock Braking System (ABS) but the trailer is not, the ABS will still improve the driver's steering control. The driver should keep an eye on the trailer and let up on the brakes if the trailer begins to swing out.

15. The most common type of foundation brake used is the:
S-cam drum brake.
C-cam drum brake.
G-cam disc brake.
P-cam disc brake.

The most common type of foundation brake is an s-cam drum brake.

16. During a static leakage test, the maximum leakage rate for a triple combination vehicle with air brakes is ____ in a minute.
3 psi
5 psi
7 psi
9 psi

When performing a static leakage test on a triple combination vehicle with air brakes, the leakage rate should be no more than 5 psi in one minute. If air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.

17. What can happen if the air pressure gets too low in an air brake system?
The brakes may squeak.
The brakes may not work.
The brakes may be sluggish.
The brakes will be very sensitive.

Pressing and releasing the brake pedal unnecessarily can let air out faster than the compressor can replace it, reducing the available air pressure. If the air pressure in an air brake system gets too low, the brakes will no longer work.

18. A low air pressure warning signal should activate:
When tank pressure falls below 120 psi.
When tank pressure falls below 60 psi.
When tank pressure falls below 10 psi.
When tank pressure falls below 5 psi.

In an air brake system, a low air pressure warning signal must come on if air pressure in the tanks falls below 60 psi. This warning signal may come in the form of a light, a buzzer, or a wig wag.

19. Do not use the parking brake when parking if:
The brakes are very hot.
The brakes are very cold.
There is snow on the ground.
There is water on the ground.

A parking brake should not be used if the vehicle's brakes are very hot from use on a steep downgrade or if the brakes are very wet and temperatures are freezing. Using the parking brake when brakes are hot could cause damage to the brakes, and using the brakes when they are wet in freezing weather may cause the brakes to ice up, rendering the vehicle immobile.

20. The emergency brake system uses:
Only parts of the parking brake system.
Only parts of the service brake system.
Parts of both the parking and service brake systems.
Only parts unique to the emergency brake system.

In an air brake system, there are three different braking systems: a service brake system, a parking brake system, and an emergency brake system. The emergency brake system uses parts of both the parking and service brake systems.

21. A vehicle equipped with an Anti-Lock Braking System (ABS) uses a ____ light to warn that the system is not working properly.
Green
Yellow
Orange
White

Anti-Lock Braking System (ABS) malfunction lamps are usually yellow. Even if the ABS isn't working properly, a driver will still have access to the vehicle's usual braking functions.

22. A tank endorsement is:
Only required when transporting gases.
Only required when transporting liquids.
Required to transport both liquids and gases.
Optional when transporting hazardous materials.

Subject to certain conditions, a tank endorsement is required to operate a tank vehicle that is used to haul either liquids or gases.

23. The ____ tells a driver how much pressure is in the air tanks.
Application pressure gauge
Air compressor governor
Supply pressure gauge
Drum brake

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.

24. If braking at a speed of 55 mph while driving on dry pavement, the brake lag can add ____ to your vehicle's total stopping distance.
32 feet
15 feet
50 feet
10 feet

The total stopping distance for vehicles equipped with air brakes is made up of four factors: perception distance, reaction distance, brake lag distance, and braking distance. When braking at a speed of 55 mph while driving on dry pavement, the brake lag can add around 32 feet to a vehicle's total stopping distance.

25. When the spring brakes are activated in a vehicle with air brakes, you should never:
Turn on the lights.
Turn the vehicle off.
Push the brake pedal down.
Open the trailer doors.

In a vehicle with air brakes, never push the brake pedal down when the spring brakes are activated. The combined force of the springs and the pressure of the air brakes could damage the brakes.

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