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 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. If using air tanks with manually operated drains, how often should you drain the tanks?

Every day

Once a week

Once a month

Once every six months

In an air brake system with manually operated drains, the tanks should be drained at the end of each day of driving.

14. When starting a vehicle with dual air brakes, pressure of ____ should be built up in the system before it is driven.

10 psi

25 psi

100 psi

200 psi

Before driving a vehicle with a dual air brake system, allow time for the air compressor to build up pressure of at least 100 psi in both the primary and secondary systems.

15. Do not use the parking brake when parking if:

The brakes are very hot.

The brakes are very cold.

There is snow on the ground.

There is water on the ground.

A parking brake should not be used if the vehicle's brakes are very hot from use on a steep downgrade or if the brakes are very wet and temperatures are freezing. Using the parking brake when brakes are hot could cause damage to the brakes, and using the brakes when they are wet in freezing weather may cause the brakes to ice up, rendering the vehicle immobile.

16. If the low pressure warning light comes on while you are driving:

Braking will only be possible if there is still enough air in the tanks.

You can apply the brakes 14 times before the air in the system runs out.

You should continue to drive normally and check the brake system when it is convenient.

You should stay at least 100 feet away from other vehicles.

When driving a vehicle with air brakes, if the low air pressure warning light comes on, it is important for you to stop and safely park your vehicle as soon as possible. There may be a leak in the system. Controlled braking will remain possible only as long as there is enough air left in the tanks.

17. When operating a vehicle with a dual brake system, a driver should:

Let the vehicle warm up before driving to ensure that fuel reaches the engine.

Wait to begin driving until the air compressor builds up a minimum pressure of 100 psi in both the primary and secondary systems.

Begin driving just after the vehicle starts.

Pump the pedal about 20 times to build pressure, then begin driving.

Before driving a vehicle with a dual air system, allow time for the air compressor to build up a minimum pressure of 100 psi in both the primary and secondary systems.

18. The safety valve located on the first tank opens:

Regularly.

If there is too little pressure.

If there is too much pressure.

After every stop.

In an air brake system, the first tank that receives compressed air has a safety valve that releases air if the pressure gets too high. It is usually set to open at 150 psi. If the valve must open, there is a fault in the system that should be repaired by a mechanic.

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