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 questions. Each question has three or four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Montana 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
Passing Score
13. 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."
14. Where is the safety relief valve usually located?
Explanation
An air brake system's safety relief valve is located in the tank that is first to receive air from the compressor.
15. How should you test the low pressure warning signal?
Explanation
It is essential that your low pressure warning light functions properly. After allowing the system to charge, you can test the warning signal by rapidly applying and releasing the brake pedal. This will release air from the braking system and the warning signal should come on when pressure drops to a dangerous level.
16. During an applied leakage test, the maximum leakage rate for a double combination vehicle is:
Explanation
It is important to know the maximum air loss rate that is safe for your specific vehicle. A double combination vehicle should have a leakage rate no higher than 4 psi in a minute during an applied leakage test.
17. What is often found in compressed air?
Explanation
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. Tanks must be drained regularly to remove this build-up.
18. In a newer vehicle, you apply the parking brake:
Explanation
