Air Brakes

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This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a..

This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a 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 Texas Commercial Motor Vehicle Drivers Handbook. Questions come from chapters covering: Air Brakes. The Air Brakes endorsement may be used with the Class A, B or C CDL.

Passing grade:

The air pressure in a dual air brake system should build from 85 to 100 psi within:

Explanation
When inspecting a vehicle with a dual air brake system, you should wait for air pressure to build from 85 to 100 psi in both the primary and secondary systems. This should take about 45 seconds.

Failing to drain the tanks in an air brake system can result in:

Explanation
In an air brake system, the air storage tanks must be drained to remove accumulated water and compressor oil. Failing to do this can cause damage. For example, water that has built up in the system could freeze in cold weather and cause brake failure.

If the brake pads rub against the brake drums and create too much heat:

Explanation
Brakes heat up with use. If they are overused and become too hot, expansion and chemical changes will make them less effective and eventually cause them to stop working altogether. This is known as "brake fade."

Vehicles with dual air brake systems:

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

A vehicle equipped with an Anti-Lock Braking System (ABS) uses a ____ light to warn that the system is not working properly.

Explanation
Anti-Lock Braking System (ABS) malfunction lamps are usually yellow. Even if the ABS isn't working properly, a driver will still have access to the vehicle's usual braking functions.

During a static leakage test, the maximum leakage rate for a triple combination vehicle with air brakes is ____ in a minute.

Explanation
When performing a static leakage test on a triple combination vehicle with air brakes, the leakage rate should be no more than 5 psi in one 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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