Trivia Quiz: Take The CDL Air Brakes Endorsement Practice Test!

20 Questions | Attempts: 8572

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Air Brake Quizzes & Trivia

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.


Questions and Answers
  • 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

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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

  • 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

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

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