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 Louisiana 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

19. Once the air tanks are at an air pressure level of 125 psi, the air compressor governor will:

Stop the compressor from pumping air.

Release air from the tanks.

Begin pumping air into the tanks.

An air compressor governor will stop the compressor from pumping air once the air tanks are at an air pressure level around 125 psi. This air pressure level is referred to as the "cut-out" level.

20. What tells you how much pressure is in your vehicle's air tanks?

The supply pressure gauge

The ABS malfunction lamp

The tractor protection valve

A vehicle that is equipped with air brakes must also be equipped with a supply pressure gauge. This gauge tells the driver how much air pressure is in each of the vehicle's air tanks.

21. When operating a vehicle with a dual air brake system, the driver should:

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

Let the air compressor build up a minimum of 100 psi pressure in the primary and secondary systems before driving.

Begin driving just after the vehicle starts.

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

22. The rods in S-cam brakes move the slack adjusters when air pressure is added to the brake chambers. This air pressure is added to the chambers when the driver:

Presses the brake pedal.

Uses the emergency brake.

Uses the trailer hand valve.

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.

23. What does an air compressor do in an air brake system?

It pumps air into the air storage tanks.

It fills the tires.

It moves air to the back of the truck.

In an air brake system, the air compressor pumps air into the air storage tanks. The air compressor is controlled by the air compressor governor.

24. 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.

25. During an inspection, slack adjusters on S-cam brakes should not move more than:

One foot.

One centimeter.

One inch.

Check each slack adjuster after parking on level ground, setting wheel chocks, and disengaging the parking brake. Pull the slack adjusters to make sure they do not move more than about one inch from where the push rod is attached. If they move more than one inch, they may be out of adjustment and will need to be fixed.

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