CDL Air Brakes Practice Test

Instructions:

This practice test consists of 20 multiple-choice questions designed to help you prepare for the CDL Air Brakes endorsement test. Choose the best answer for each question.

1. What is the main purpose of the air brakes system?

A) To provide smoother ride comfort
B) To assist with steering
C) To stop the vehicle using compressed air
D) To increase fuel efficiency

2. What are the three main components of an air brake system?

A) Compressor, regulator, and filter
B) Air compressor, air tanks, and brake shoes
C) Governor, parking brake, and emergency brake
D) Service brake, parking brake, and emergency brake

3. At what PSI does the safety valve typically open in an air brake system?

A) 100 PSI
B) 125 PSI
C) 150 PSI
D) 175 PSI

4. What should you do if your air pressure drops below the minimum level?

A) Speed up to build more pressure
B) Stop and safely park the vehicle
C) Use the parking brake immediately
D) Continue driving but monitor the pressure gauge closely

5. What is the function of the air compressor in the air brake system?

A) To maintain air pressure in the tires
B) To supply compressed air to the air storage tanks
C) To control the braking force applied
D) To cool the brakes during heavy use

6. What does the air pressure gauge indicate?

A) The pressure in the air tanks
B) The pressure applied to the brake pedal
C) The pressure in the tires
D) The temperature of the brake drums

7. When should the low air pressure warning signal come on?

A) At 100 PSI
B) Between 55 and 75 PSI
C) At 85 PSI
D) Between 45 and 65 PSI

8. What is the purpose of the spring brakes?

A) To assist with emergency braking
B) To automatically apply the brakes when air pressure is too low
C) To provide better stopping power on slippery surfaces
D) To increase braking force on downhill grades

9. What is a “dual air brake system”?

A) A system that uses both air and hydraulic brakes
B) A system with two separate air brake circuits
C) A system that allows you to use brakes with either foot
D) A system that controls brakes on both front and rear axles

10. Why is it important to drain air tanks regularly?

A) To remove moisture and oil buildup
B) To increase the pressure in the tanks
C) To decrease braking power
D) To maintain the temperature of the air in the tanks

11. What happens when you press the brake pedal in an air brake system?

A) Air pressure decreases in the brake chambers
B) The air compressor stops running
C) Air pressure increases in the brake chambers
D) Air is released from the air tanks

12. How can you test the low air pressure warning signal?

A) Step on and off the brake pedal to reduce air pressure
B) Fully charge the air system, then shut off the engine and step on the brake pedal
C) Drive at high speeds and apply the brakes suddenly
D) Pump the brakes while the vehicle is parked

13. What should you do if the air compressor governor cuts out too soon?

A) Adjust your driving speed
B) Drive with caution until you can repair the system
C) Report the issue and have it repaired before driving
D) Pump the brakes to increase pressure

14. What is the maximum leakage rate for a straight truck or bus with the engine off and brakes released?

A) 2 PSI per minute
B) 3 PSI per minute
C) 4 PSI per minute
D) 6 PSI per minute

15. How often should you check the slack adjusters in your vehicle?

A) Every 10,000 miles
B) Monthly
C) During every pre-trip inspection
D) Annually

16. What is the “cut-in” pressure for an air compressor?

A) 60 PSI
B) 90 PSI
C) 100 PSI
D) 125 PSI

17. Why is it dangerous to ride the brakes for a long period of time?

A) It can cause the brakes to overheat and fail
B) It decreases fuel efficiency
C) It can cause the air compressor to fail
D) It increases wear on the tires

18. What should you do if the air pressure warning signal comes on while driving?

A) Continue driving until you reach a repair shop
B) Exit the highway immediately and find a safe place to park
C) Apply the parking brake to stop the vehicle
D) Increase your speed to regain air pressure

19. What is the main purpose of the service brakes?

A) To assist with parking on inclines
B) To bring the vehicle to a complete stop during normal driving
C) To automatically stop the vehicle in an emergency
D) To help with backing up the vehicle

20. How can you check that the spring brakes come on automatically?

A) By pulling the parking brake knob and listening for a click
B) By reducing air pressure to the range where the spring brakes activate
C) By stepping on the brake pedal with the engine off
D) By accelerating quickly and then braking

Answer Key:

This practice test is designed to provide a comprehensive review of the key concepts you’ll need to understand to pass the CDL Air Brakes endorsement test. Reviewing these questions and answers carefully will help you identify areas where you may need further study. For more resources and practice tests, visit FreightRelocators.com.

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