CDL Air Brakes Practice Test 4

This is a timed quiz. You will be given 45 seconds per question. Are you ready?

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Which device allows you to remove oil and water from the air brake systems?

Correct! Wrong!

Air tank drain. The air tank drains allow you to drain oil and moisture from the air tanks. An alcohol evaporator puts alcohol into the air system to help reduce the risk of ice in cold weather. A safety valve protects the tank and system from too much pressure. The treadle valve is another name for the brake pedal

What does it mean when the safety valve opens and releases air?

Correct! Wrong!

A and C. The safety relief valve protects the tanks and the air brake system from too much pressure. It is designed to open at 150 psi. If the valve releases air, a mechanic should check the system.

What should the air pressure loss be in a single vehicle with a fully charged air system?

Correct! Wrong!

Less than 2 psi per minute. For single vehicles the loss rate should be less than 2 psi per minute. For combination vehicles, the loss rate should be less than 3 psi per minute.

In a combination vehicle, what should the air pressure loss be with a fully charged air system?

Correct! Wrong!

Less than 3 psi per minute. For combination vehicles, the loss rate should be less than 3 psi per minute. For single vehicles the loss rate should be less than 2 psi per minute.

Where is compressed air stored?

Correct! Wrong!

Main reservoirs. The main reservoirs are also known as the air storage tanks and store the compressed air produced by the air compressor.

Which of the following devices indicates how much air pressure you are applying to your brakes?

Correct! Wrong!

Application pressure gauge. Some vehicles with air brakes have an application pressure gauge that tells you how much pressure you are applying to the brakes. All vehicles with air brakes have a supply pressure gauge that indicates how much pressure is in the air tanks. The low air pressure warning signal will only indicate when you have low air pressure (below 60 psi). The governor controls when the air compressor will pump air into the air storage tanks.

Which of the following devices can be used as the low air pressure warning signal?

Correct! Wrong!

Any of the above. A low pressure warning signal comes on when the air pressure falls below 60 psi. The signal is usually a red light, which may be accompanied by a buzzer. A mechanical arm, known as a wig wag, can also be used.

What is a wig-wag?

Correct! Wrong!

A mechanical arm that comes into view when the air pressure falls below 60 psi. A wig-wag is a type of low pressure air signal. A front brake limiting valve cuts the normal air pressure to the front brakes by half. A treadle valve is another name for a brake pedal. A modulating control valve is a lever used to apply the spring brakes gradually.

What is a modulating control valve?

Correct! Wrong!

A lever used to apply the spring brakes gradually. The modulating control valve is found on the dash of some vehicles. It is used to apply the spring brakes gradually. A front brake limiting valve cuts the normal air pressure to the front brakes by half. An air compressor governor controls when the air compressor will pump air into the air storage tanks. An air tank drain is used to drain oil and water from the air storage tanks.

What does the Air Compressor Governor control?

Correct! Wrong!

When the air compressor pumps air into the storage tanks. The front brake limiting valve is used to cut air pressure to the front brakes. An automatic air tank drain is used to automatically expel water and oil from the storage tanks.

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