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 three answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Idaho Commercial Driver’s 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. Brakes can get out of adjustment:

If they are hot.

During the winter.

If they are used at all.

If brakes on one side are used more often than brakes on the other side.

Brakes are particularly prone to getting out out adjustment if they are hot. Use proper braking techniques to avoid letting your brakes overheat.

14. What is removed when an air tank is drained?

Water and oil

Ammonia

Wood

Chlorine

In an air brake system, the air storage tanks are equipped with drains to allow water and compressor oil to be removed. The water and oil can damage the brakes if left to accumulate in the system.

15. Why should you regularly drain the air tanks?

Because the air gets old and needs to be replaced

Because compressed air contains some water and the water collects in the tanks

To allow for a change in pressure

Compressed air usually contains a certain amount of moisture and compressor oil, which can build up in the air storage tanks and damage the brake system. The tanks should be drained to clean out these accumulations. On a tank with a manual drain valve, draining should be performed at the end of each day of driving.

16. If the low air pressure warning signal comes on, you should:

Continue driving, but have the brakes repaired within a week.

Pull over and inspect the brakes.

Phone a mechanic while driving.

If the low air pressure warning signal comes on while you are driving a vehicle with air brakes, you should immediately bring the vehicle to a safe stop while you are still able to control the brakes. Inspect and repair the brakes as soon as possible.

17. Air tank drains should:

Not be used by the driver.

Only be used when it is wet outside.

Be used to drain the tanks completely.

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.

18. A ____ allows a driver to gradually apply spring brakes.

Modulating control valve

Trailer air supply control

Relay valve

A modulating control valve allows a driver to gradually apply spring brakes. In equipped vehicles, the valve is controlled by a lever located on the dashboard.

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