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Tennessee CDL DMV Air Brakes 2

Take 6 practice tests for CDL is the best way to prepare for your Tennessee DMV exam is by taking our free practice tests. The following question are from real Tennessee 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. While operating on a downgrade, you should brake until you reach a speed that is:
5 mph below your safe speed.
10 mph below your safe speed.
15 mph below your safe speed.

While driving downhill, you should hold down the brake pedal until your vehicle reaches a speed 5 mph below your safe speed, then release the brake pedal. Repeat this process.

2. 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.

3. If one air system in a dual air brake system is very low on pressure:
None of the brakes will work at all.
Either the front or rear brakes will not be operating fully.
There will be no noticeable affect.
Lights on the outside of the tractor will flash.

In a dual air brake system, if one of the air systems gets very low on pressure, either the front or rear brakes will not be operating fully. You should bring your vehicle to a safe stop and have the air system repaired.

4. Pressing and releasing a brake pedal unnecessarily can:
Release air faster than it can be replaced.
Add more air to the braking system.
Make the brake pedal more sensitive.
Create a loud noise.

In an air brake system, pressing and releasing the brake pedal unnecessarily can release air from the braking system faster than the compressor can replace it.

5. 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.

6. If the low air pressure warning signal comes on in a vehicle with air brakes, the driver should:
Test the brakes while driving, but continue driving if nothing seems wrong.
Immediately stop driving.
Drive with the hazard lights activated.

If the low air pressure warning signal comes on while you are operating a vehicle with air brakes, you should stop and safely park the vehicle as soon as possible. It is essential that you are able to stop safely while you still have some braking power remaining.

7. The rods in S-cam brakes move the slack adjusters when air pressure is added to the brake chambers. This air pressure is added to the chambers when the driver:
Presses the brake pedal.
Uses the emergency brake.
Uses the trailer hand valve.

When pressing the brake pedal in a vehicle with S-cam brakes, air will enter the brake chambers. The added air pressure will push out the rods and move slack adjusters, twisting the brake camshafts.

8. To stop a vehicle using air brakes:
The brake pedal should be pressed.
The brake pedal should be lifted.
The brake knob should be pulled out.
The brake knob should be pushed in.

To stop normally in a vehicle with air brakes, press down the brake pedal.

9. 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.

10. An air compressor governor will stop the compressor from pumping air once the air tanks have an air pressure level of:
125 psi.
100 psi.
150 psi.
80 psi.

An air compressor governor will stop the compressor from pumping air once the air tanks are at an air pressure level of 125 psi. This air pressure level is referred to as the "cut-out" level.

11. What helps prevent wheel lockup when braking?
An Anti-Lock Braking System (ABS)
Air brakes
An alternator

The purpose of an Anti-Lock Braking System (ABS) is to prevent wheel lockup while brakes are being applied.

12. 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.

13. When you need to stop in an emergency, you should:
Lock the wheels and skid to a stop.
Stop in a way that keeps your vehicle in a straight line.
Stop in a way that turns your vehicle.
Expect your vehicle to slow down more quickly than usual.

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 traveling in a straight line while still allowing you to turn, if necessary.

14. What does an air compressor do in an air brake system?
It pumps air into the air storage tanks.
It fills the tires.
It moves air to the back of the truck.

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.

15. During an applied leakage test, the maximum leakage rate for a double combination vehicle is ____ in a minute.
2 psi
4 psi
6 psi

It is important to know the maximum air loss rate that is safe for your specific vehicle. A double combination vehicle should have a leakage rate no higher than 4 psi in a minute during an applied leakage test.

16. In a dual air brake system:
Air tanks are shared between both systems.
Each system has its own air tanks.
You must designate which system you are using.

There are two air brake systems in a dual air brake system. The systems share a set of brake controls, but each system has its own tanks, hoses, and lines.

17. What color light indicates a vehicle's ABS is not working?
Green
Blue
Yellow

On vehicles with Anti-Lock Braking Systems (ABS), yellow malfunction lamps alert the driver to ABS malfunction.

18. In cold weather, an alcohol evaporator should be checked and filled:
Once a week.
Every day.
Every hour.
Once a month.

An alcohol evaporator can help prevent ice from building up in an air brake system. In cold weather, the evaporator should be checked and refilled every day.

19. An alcohol evaporator is especially important:
In cold weather.
In hot weather.
In dry weather.

Some air brake systems contain an alcohol evaporator. This evaporator introduces alcohol into the system to help prevent ice from forming in cold weather.

20. Vehicles with dual air brake systems:
Maintain full-capacity air pressure in the braking systems even when the vehicle is not running.
Maintain some air pressure in the braking systems when the vehicle is not running.
Must be run to build enough air pressure to brakes to operate properly.
Do not need time to build air pressure before a trip.

Before driving a vehicle with a dual air brake system, you must allow the air compressor time to build up at least 100 psi of air pressure in both the primary and secondary systems.

21. If the safety relief valve in the air brake system releases air:
The compressor needs more air.
The air pressure has become too high.
The brakes are fully operational.

An air brake system has a safety relief valve, which releases air from the tanks if the pressure gets too high. If the valve must operate, something in the system is wrong and should be addressed by a mechanic.

22. 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.

23. 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.

24. The application pressure gauge:
Shows how much air pressure is being applied to the brakes.
Shows the temperature of air being used in the braking system.
Shows the pressure of the air coming from the compressor.
Shows the number of times the brakes have been used.

In an air brake system, the application pressure gauge shows how much air pressure is being applied to the brakes. Not all vehicles with an air brake system have this gauge.

25. Friction in an S-cam brake is caused when the brake shoes and linings:
Press against the outside of the brake drum.
Press against the inside of the brake drum.
Push against each other.

Friction inside a brake drum is caused when the brake shoes and linings push against the inside of the drum. The friction in the drums will slow and stop the vehicle.

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