Texas CDL Air Brakes Exam Questions and
Answers 2025
1. What is the purpose of the air compressor in an air brake system?
A) To maintain pressure in the brake system
B) To control the speed of the truck
C) To cool the brake components
D) To filter air before it enters the system
Answer: A) To maintain pressure in the brake system
Explanation: The air compressor is responsible for maintaining the correct
pressure in the brake system by compressing air and storing it in the air tanks.
2. Which of the following is a common cause of air brake failure?
A) Low tire pressure
B) Excessive air pressure
C) Insufficient air supply or leaks
D) High coolant temperature
Answer: C) Insufficient air supply or leaks
,Explanation: A leak in the air system or insufficient air supply can result in brake
failure. Proper maintenance of the air system is crucial.
3. In a dual air brake system, the primary air system controls which brakes?
A) The parking brakes
B) The front brakes
C) The rear brakes
D) The emergency brakes
Answer: B) The front brakes
Explanation: In a dual air brake system, the primary air system typically controls
the front brakes, while the secondary air system controls the rear brakes.
4. What does the low air pressure warning signal indicate?
A) The air tanks are full
B) The vehicle is ready for brake application
C) Air pressure is too low to safely apply the brakes
D) The air pressure is in the normal range
Answer: C) Air pressure is too low to safely apply the brakes
Explanation: A low air pressure warning signal activates when the air pressure
drops below a safe level, indicating that the air brake system might not work
properly.
, 5. What is the purpose of the brake pedal in an air brake system?
A) To engage the parking brake
B) To release air from the system
C) To apply air pressure to the brakes
D) To test the air pressure
Answer: C) To apply air pressure to the brakes
Explanation: The brake pedal is used to apply air pressure to the brake system,
activating the brakes.
6. How do you test the air brakes for leaks on a vehicle?
A) Release the parking brake and press the brake pedal
B) Turn off the engine, then pump the brake pedal to check for a drop in
pressure
C) Increase the engine RPM and check the brake system
D) Check the air tank pressure with the engine running
Answer: B) Turn off the engine, then pump the brake pedal to check for a drop in
pressure
Explanation: By turning off the engine and pumping the brake pedal, you can
test for any significant drop in pressure, which indicates a potential air leak.
7. What should you do if you notice that the air pressure gauge drops below 60 psi
during operation?
Answers 2025
1. What is the purpose of the air compressor in an air brake system?
A) To maintain pressure in the brake system
B) To control the speed of the truck
C) To cool the brake components
D) To filter air before it enters the system
Answer: A) To maintain pressure in the brake system
Explanation: The air compressor is responsible for maintaining the correct
pressure in the brake system by compressing air and storing it in the air tanks.
2. Which of the following is a common cause of air brake failure?
A) Low tire pressure
B) Excessive air pressure
C) Insufficient air supply or leaks
D) High coolant temperature
Answer: C) Insufficient air supply or leaks
,Explanation: A leak in the air system or insufficient air supply can result in brake
failure. Proper maintenance of the air system is crucial.
3. In a dual air brake system, the primary air system controls which brakes?
A) The parking brakes
B) The front brakes
C) The rear brakes
D) The emergency brakes
Answer: B) The front brakes
Explanation: In a dual air brake system, the primary air system typically controls
the front brakes, while the secondary air system controls the rear brakes.
4. What does the low air pressure warning signal indicate?
A) The air tanks are full
B) The vehicle is ready for brake application
C) Air pressure is too low to safely apply the brakes
D) The air pressure is in the normal range
Answer: C) Air pressure is too low to safely apply the brakes
Explanation: A low air pressure warning signal activates when the air pressure
drops below a safe level, indicating that the air brake system might not work
properly.
, 5. What is the purpose of the brake pedal in an air brake system?
A) To engage the parking brake
B) To release air from the system
C) To apply air pressure to the brakes
D) To test the air pressure
Answer: C) To apply air pressure to the brakes
Explanation: The brake pedal is used to apply air pressure to the brake system,
activating the brakes.
6. How do you test the air brakes for leaks on a vehicle?
A) Release the parking brake and press the brake pedal
B) Turn off the engine, then pump the brake pedal to check for a drop in
pressure
C) Increase the engine RPM and check the brake system
D) Check the air tank pressure with the engine running
Answer: B) Turn off the engine, then pump the brake pedal to check for a drop in
pressure
Explanation: By turning off the engine and pumping the brake pedal, you can
test for any significant drop in pressure, which indicates a potential air leak.
7. What should you do if you notice that the air pressure gauge drops below 60 psi
during operation?
