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. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Illinois Commercial Driver’s License Study Guide. Questions come from chapters 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

1. A dual air brake system:

Has a single air brake system, but uses two sets of controls.

Has one air brake system for each side of the truck.

Has two brakes for each wheel.

Has two separate air brake systems, but uses a single set of controls.

A dual air brake system has two separate air brake systems that use a single set of brake controls. One system typically operates the regular brakes on the rear axle or axles. The other system operates the regular brakes on the front axle.

2. On a truck with air brakes, the braking system’s air compressor:

Pumps air into the air storage tanks.

Fills the tires.

Moves air to the back of the truck.

Cleans the brakes.

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.

3. Air tank drains:

Allow rain water to enter the tanks.

Are used to drain water and oil from the tanks.

Should never be opened.

Must remain open while driving.

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.

4. When inspecting your brakes, a slack adjuster should move ____ from where it is attached to the push rod.

At least three inches

More than two inches

Up to five inches

No more than one inch

Check each slack adjuster after 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.

5. Most heavy-duty vehicles use:

Single air brake systems.

Dual air brake systems.

Triple air brake systems.

Quadruple air brake systems.

Most heavy-duty vehicles use dual air brake systems, in which there are two separate braking systems operated by a single set of controls. Each system operates the brakes on different axles.

6. During a static leakage test, the maximum leakage rate for a single vehicle with air brakes is ____ in one minute.

1 psi

2 psi

3 psi

4 psi

When performing a static leakage test on a single vehicle with air brakes, the leakage rate should be no more than 2 psi in a minute. If air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.

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