Trivia Quiz: Take The CDL Air Brakes Endorsement Practice Test!
These questions are taken from actual CDL licensing tests. If you can reliably pass this practice test, you will have no trouble passing the real test.
- 1.
Why must air tanks be drained?
- A.
To drain all the air out of the tank.
- B.
To drain moisture and oil out of the tank.
- C.
To keep anyone from moving the vehicle.
- D.
To prevent leakage
Correct Answer
B. To drain moisture and oil out of the tank.Explanation
Air tanks must be drained to remove moisture and oil that can accumulate inside the tank. Moisture and oil can condense and collect in the tank over time, which can lead to corrosion and damage to the tank and other components of the air system. Draining the tank regularly helps to prevent these issues and ensures the proper functioning of the air system.Rate this question:
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- 2.
What is a supply pressure gauge used for?
- A.
To tell you how much diesel is in the vehicle.
- B.
To tell you how much water is in the air tank.
- C.
To tell you how much air is in the air tank.
- D.
To tell you how much air is in the tires.
Correct Answer
C. To tell you how much air is in the air tank.Explanation
A supply pressure gauge is used to measure the amount of air in the air tank. This is important information as it allows the user to monitor the pressure level and ensure that it is within the desired range. By knowing the air pressure in the tank, the user can also determine if there is enough air for the intended application or if additional air needs to be added.Rate this question:
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- 3.
Modern air brake systems combine three different components. The components are Service Brakes, Parking Brakes, and:
- A.
S-cam brakes.
- B.
Drum brakes.
- C.
Emergency brakes.
- D.
Foot brakes.
Correct Answer
C. Emergency brakes.Explanation
Modern air brake systems combine three different components: Service Brakes, Parking Brakes, and Emergency Brakes. Emergency brakes are an essential part of air brake systems as they provide an additional braking mechanism in case of emergencies. These brakes are designed to engage quickly and with maximum force to help stop the vehicle in critical situations. They act as a safety measure and are crucial for ensuring the overall effectiveness and reliability of the braking system.Rate this question:
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- 4.
Oil and water usually collect in compressed air tanks. If you do not have an automatic tank drain, when should you drain the air tanks?
- A.
After every working day.
- B.
Once a week.
- C.
After every four hours of service.
- D.
Every other week.
Correct Answer
A. After every working day.Explanation
Oil and water tend to accumulate in compressed air tanks over time. Draining the air tanks after every working day helps to prevent the build-up of these contaminants, ensuring the efficient and safe operation of the compressed air system. Regular draining of the air tanks helps to maintain the quality of the compressed air and prevent any potential damage or malfunctions caused by the presence of oil and water.Rate this question:
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- 5.
Why drain water from the compressed air tanks?
- A.
The low boiling point of water reduces braking power.
- B.
Water will foul the air compressor oil.
- C.
Water can freeze in cold weather and cause brake failure.
- D.
Water over cools the compressor.
Correct Answer
B. Water will foul the air compressor oil.Explanation
Water will foul the air compressor oil because when water mixes with oil, it forms a sludge-like substance that can clog the air compressor and reduce its efficiency. This can lead to poor performance of the compressed air system and potential damage to the equipment. Removing water from the compressed air tanks helps to prevent this issue and ensures the proper functioning of the air compressor.Rate this question:
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- 6.
Air brake equipped vehicles must have:
- A.
An air use gauge.
- B.
At least two brake heaters.
- C.
A backup hydraulic system.
- D.
A supply pressure gauge.
Correct Answer
D. A supply pressure gauge.Explanation
Air brake equipped vehicles must have a supply pressure gauge because it is essential to monitor the pressure in the air brake system. The supply pressure gauge allows the driver to ensure that there is enough pressure to operate the brakes effectively. If the pressure drops below a certain level, it can indicate a leak or other issue in the system that needs to be addressed. Therefore, a supply pressure gauge is crucial for maintaining the safety and functionality of the air brakes on a vehicle.Rate this question:
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- 7.
With the engine off and the brakes on, air loss in a straight truck or bus should not be more than ________
- A.
1 psi in 30 seconds.
- B.
1 psi in one minute.
- C.
2 psi in 45 seconds.
- D.
3 psi in one minute.
Correct Answer
D. 3 psi in one minute.Explanation
When the engine is off and the brakes are applied, the air loss in a straight truck or bus should not exceed a certain limit. This is because the air pressure in the brake system should remain relatively stable. The correct answer of 3 psi in one minute suggests that any air loss beyond this rate would indicate a potential issue with the brake system, such as a leak. This limit ensures that the brakes will still function properly and maintain sufficient air pressure for safe operation.Rate this question:
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- 8.
When making an emergency stop using the stab braking method, you will:
- A.
Pump the brake pedal rapidly and lightly.
- B.
Brake as hard as possible until the wheels lock, then release the brakes for as much time as the wheels were locked.
- C.
Brake as hard as possible until the wheels lock, then release the brakes until the wheels start rolling, and repeat.
- D.
Press hard on the brake pedal and apply full hand valve until you stop.
Correct Answer
C. Brake as hard as possible until the wheels lock, then release the brakes until the wheels start rolling, and repeat.Explanation
When making an emergency stop using the stab braking method, the correct approach is to brake as hard as possible until the wheels lock, then release the brakes until the wheels start rolling, and repeat. This technique helps to maintain control of the vehicle while still allowing for maximum braking force. By releasing the brakes when the wheels lock, the driver can prevent the vehicle from skidding and maintain traction. The process of repeating the braking and releasing action helps to bring the vehicle to a stop in the shortest possible distance.Rate this question:
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- 9.
A sign of brakes fading is:
- A.
Pressure on the brake pedal is released and speed increases.
- B.
You have to push harder on the brake pedal to control your speed on a downgrade.
- C.
The brake feels spongy when pressure is applied.
- D.
Less pressure is needed on the brake pedal for each stop.
Correct Answer
B. You have to push harder on the brake pedal to control your speed on a downgrade.Explanation
When brakes start to fade, it means that they are losing their effectiveness. This can be caused by overheating or wearing out of the brake pads. As a result, when going downhill (a downgrade), the brakes may not be able to provide enough stopping power, requiring the driver to push harder on the brake pedal to control the speed. This is a sign that the brakes are fading and need attention.Rate this question:
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- 10.
To check the free play of manual slack adjusters on s-cam brakes you must:
- A.
Park on level ground, chock the wheels, and release the parking brakes.
- B.
Stop on level ground and apply the parking brakes.
- C.
Park on level ground and drain off air pressure before adjusting.
- D.
Park on a slight grade, release the parking brake, apply the service brakes, and check for vehicle movement.
Correct Answer
A. Park on level ground, chock the wheels, and release the parking brakes. -
- 11.
If the air compressor develops a leak, what keeps the air in the tanks?
- A.
The tractor protection valve.
- B.
The emergency relay valve.
- C.
The one way check valve.
- D.
The air compressor.
Correct Answer
C. The one way check valve.Explanation
The one way check valve is responsible for keeping the air in the tanks if the air compressor develops a leak. This valve allows air to flow into the tanks from the compressor, but prevents air from flowing back out of the tanks. Therefore, even if there is a leak in the air compressor, the one way check valve ensures that the air remains in the tanks and does not escape.Rate this question:
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- 12.
When driving down a long steep hill, you should:
- A.
Use stab braking.
- B.
Begin braking when you are 10 M.P.H above your safe speed.
- C.
Release the brake when you are 5 M.P.H below your safe speed.
- D.
Use the trailer brakes.
Correct Answer
C. Release the brake when you are 5 M.P.H below your safe speed.Explanation
When driving down a long steep hill, it is important to release the brake when you are 5 M.P.H below your safe speed. This is because if you continuously apply the brake, it can cause the brakes to overheat and potentially fail. By releasing the brake when you are slightly below your safe speed, you allow the vehicle to naturally slow down and prevent excessive wear on the brakes. This technique helps to maintain control and prevent any potential accidents or damage to the vehicle.Rate this question:
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- 13.
The most common type of foundation brakes found on heavy vehicles is the:
- A.
Disc brakes
- B.
Wedge drum
- C.
S-cam drum
- D.
None of the above
Correct Answer
C. S-cam drumExplanation
S-cam drum brakes are the most common type of foundation brakes found on heavy vehicles. These brakes use a rotating camshaft, called an S-cam, to force the brake shoes against the brake drum, creating friction and stopping the vehicle. This design is widely used in heavy vehicles due to its durability and ability to handle high braking forces. Disc brakes and wedge drum brakes are also used in some vehicles, but they are not as common as S-cam drum brakes.Rate this question:
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- 14.
Vehicles with air brakes must have:
- A.
At least two air tanks
- B.
An air pressure gauge to show the pressure available for braking
- C.
An air pressure gauge to show air used by the brake chambers for braking
- D.
None of the above
Correct Answer
B. An air pressure gauge to show the pressure available for brakingExplanation
Vehicles with air brakes must have an air pressure gauge to show the pressure available for braking. This is necessary because air brakes rely on compressed air to operate effectively. The air pressure gauge allows the driver to monitor the pressure in the air tanks and ensure that there is enough pressure to engage the brakes when needed. Without this gauge, the driver would not be able to accurately determine the amount of pressure available for braking, which could compromise the safety of the vehicle.Rate this question:
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- 15.
The brake system that applies and releases the brakes when the driver uses the brake pedal is the:
- A.
Service brake system.
- B.
Emergency brake system.
- C.
Parking brake system.
- D.
None of the above.
Correct Answer
A. Service brake system.Explanation
The service brake system is responsible for applying and releasing the brakes when the driver uses the brake pedal. This system is designed to slow down or stop the vehicle during normal driving conditions. The emergency brake system, on the other hand, is used in emergency situations to stop the vehicle when the service brakes fail. The parking brake system is used to keep the vehicle stationary when parked. Therefore, the correct answer is the service brake system.Rate this question:
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- 16.
Which of the following makes the total stopping distance for air brakes longer than the stopping distance for hydraulic brakes:
- A.
Brake lag distance.
- B.
Action distance.
- C.
Perception distance.
- D.
Effective braking distance.
Correct Answer
A. Brake lag distance.Explanation
Brake lag distance is the time it takes for the air brakes to engage and start slowing down the vehicle. This delay in response increases the overall stopping distance for air brakes compared to hydraulic brakes, which have a quicker response time. Therefore, the brake lag distance is the reason why the total stopping distance for air brakes is longer than the stopping distance for hydraulic brakes.Rate this question:
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- 17.
Of the following choices, the first thing to do when a low air pressure warning comes on is:
- A.
Open the air supply control valve.
- B.
Adjust the brake pedal for more travel.
- C.
Stop and park as soon as safely possible.
- D.
Up-shift.
Correct Answer
C. Stop and park as soon as safely possible.Explanation
When a low air pressure warning comes on, it is crucial to stop and park as soon as safely possible. This warning indicates that there is a problem with the air pressure in the braking system, which can greatly affect the vehicle's ability to brake properly. Continuing to drive without addressing this issue can be extremely dangerous and increase the risk of accidents. Therefore, stopping and parking immediately allows for the necessary repairs or inspections to be carried out, ensuring the safety of both the driver and other road users.Rate this question:
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- 18.
The braking power of the spring brakes:
- A.
Can only be tested by highly trained brake service people.
- B.
Depends on the adjustment of the service brakes.
- C.
Increases when the service brakes are hot.
- D.
Is not affected by the condition of the service brakes.
Correct Answer
B. Depends on the adjustment of the service brakes.Explanation
The correct answer is "Depends on the adjustment of the service brakes." The braking power of the spring brakes is dependent on the adjustment of the service brakes. If the service brakes are not properly adjusted, it can affect the braking power of the spring brakes. Therefore, it is important to ensure that the service brakes are adjusted correctly in order to maintain the optimal braking performance of the spring brakes.Rate this question:
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- 19.
The air compressor governor is responsible for controlling:
- A.
When air is pumped into the air tanks.
- B.
Air pressure applied to the brakes.
- C.
The speed of the air compressor.
- D.
When the brake chambers release pressure.
Correct Answer
A. When air is pumped into the air tanks.Explanation
The air compressor governor is responsible for controlling the process of pumping air into the air tanks. It regulates the pressure and ensures that the air tanks are properly filled. This is important for the functioning of the air brake system as it provides the necessary compressed air for the brakes to operate effectively. By controlling the air pressure in the tanks, the governor helps maintain the optimal braking performance and ensures the safe operation of the vehicle.Rate this question:
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- 20.
The application pressure gauge shows the driver how much pressure:
- A.
Has been used on the trip.
- B.
Is in the air tanks.
- C.
Is being applied to the brakes.
- D.
None of these.
Correct Answer
C. Is being applied to the brakes.Explanation
The application pressure gauge is a device that displays the amount of pressure being applied to the brakes. This gauge helps the driver monitor and control the braking system, ensuring that the appropriate amount of pressure is applied for safe and effective braking. It does not show the pressure that has been used on the trip or the pressure in the air tanks. Therefore, the correct answer is that the application pressure gauge shows the driver how much pressure is being applied to the brakes.Rate this question:
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May 02, 2023Quiz Edited by
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Oct 06, 2010Quiz Created by
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