Instructions

Air Brakes

This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice.. Read More

This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice questions. Each question has four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Washington D.C. Commercial Driver License Manual. Questions come from the chapter covering: Air Brakes. The Air Brakes endorsement may be used with the Class A, B or C CDL.

Number of Question 25

Passing Score 20

13. 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.

14. Braking mechanisms are located ____ a brake drum.

Outside

Inside

Next to

On top of

Drum brakes are attached to the wheels and located on the axles of a vehicle. The braking mechanisms that cause the vehicle to stop can be found inside of a drum brake.

15. What can happen if parking brakes are used in very wet weather with temperatures below freezing?

The brakes will squeak.

The brakes may freeze so the vehicle cannot move.

The brakes may suddenly release by themselves.

The brakes may become too smooth to be used.

Parking brakes should not be used in very wet weather when temperatures are below freezing. The brakes could become frozen in place, making it impossible to move the vehicle.

16. When you press the brake pedal in a vehicle with S-cam brakes, air pressure pushes out the rod and moves the:

Slack adjuster.

Axle.

Brake drum.

Alcohol evaporator.

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.

17. What color are ABS malfunction lamps?

Orange

Yellow

Green

Blue

Vehicles with Anti-Lock Braking Systems (ABS) have yellow malfunction lamps.

18. Air tank drains:

Allow rain water to enter the tanks.

Are used to drain water and oil from the air tanks.

Should never be opened.

Must remain open while driving.

Compressed air in an air brake system usually contains a certain amount of water and compressor oil. The water and oil can damage the brakes if left to accumulate in the system. Manually operated air tank drains must be opened daily to remove this build-up.

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