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. 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
Passing Score
7. Air pressure should build up in a single air system within:
Explanation
In a vehicle with a single air brake system, after the engine is at operating rpms, the pressure in the air system should generally build from 50 to 90 psi within three minutes.
8. 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.
9. The parking brake should be:
Explanation
The parking brake should be applied every time you park your vehicle.
10. Water and compressor oil are usually found in the compressed air within an air brake system. Water and compressor oil:
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. Manually operated air tank drains must be opened daily to remove this build-up.
11. An Anti-Lock Braking System (ABS):
Explanation
Anti-Lock Braking Systems (ABS) are compatible with air braking systems. ABS helps maintain control of a vehicle and prevents the wheels from locking up during hard braking on slippery surfaces. ABS can still provide benefits even if is present on only one axle.
12. A one-way check valve:
Explanation
