Illinois CDL Air Brakes Practice Test (IL) 2

4.9 out of 5 (323 votes)
80% Passing score
20 Questions
4 Mistakes allowed
As an aspiring commercial driver in Illinois, you understand the importance of thorough preparation, especially when it comes to obtaining your CDL air brake endorsement. Our Illinois CDL air brake practice test is designed to provide you with the knowledge and confidence needed to ace the test. This comprehensive test consists of 20 multiple-choice questions, meticulously covering various aspects such as components, operation, safety inspections, and stopping distance calculations. The test delves into critical details, including the use of dual air brake systems, which enhance safety by offering a backup in case one system fails. To pass, you need to correctly answer at least 16 questions. In Illinois, our diverse weather conditions and bustling urban centers demand a solid understanding of air brake systems to ensure safe driving. From navigating the snowy streets of Chicago in winter to managing the busy highways connecting our vibrant communities, your preparedness will make a significant difference. The Illinois CDL air brake practice test is accessible online, whether you're using a mobile device, desktop, or our convenient mobile apps. This ease of access allows you to study anytime, anywhere, making it perfect for those with a busy schedule. By taking the Illinois CDL air brake test, you can identify any gaps in your knowledge and focus on areas that need improvement. This focused approach will help you enhance your understanding and increase your chances of passing the official test. Moreover, the Illinois CDL air brake practice test includes questions based on real-life driving scenarios. This practical aspect not only prepares you for the written test but also equips you with the skills needed to handle real-world situations on the road. Whether you're driving through the farmlands of central Illinois or the industrial zones of the Metro East, being well-versed in air brake systems is crucial for your safety and the safety of others. Start your preparation with our Illinois CDL air brake practice test today, and ensure you're fully equipped to pass the CDL air brakes endorsement test. By mastering these essential topics, you'll be well on your way to a successful and safe driving career in Illinois.
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Sample Illinois Air Brakes Test Questions

Question 1

During cold weather, how should you maintain an air-brake alcohol evaporator each day?

  1. A Drain all alcohol from the container
  2. B Lubricate the system with lightweight oil
  3. C Install a new alcohol bottle every day
  4. D Check the alcohol level and refill it as needed

Correct answer: D – Check the alcohol level and refill it as needed

The Illinois CDL Study Guide directs drivers to inspect the alcohol container daily during cold weather and add alcohol when needed. The evaporator helps reduce icing in air-brake valves and related parts. Air tanks still must be drained daily to remove water and oil unless automatic drain valves are installed.

Source: Illinois CDL Study Guide — § 5.1.5, “Alcohol Evaporator”

Question 2

What functions do spring brakes normally provide on large air-brake vehicles?

  1. A Parking braking only
  2. B Service braking only
  3. C Parking and emergency braking
  4. D Routine braking during normal driving

Correct answer: C – Parking and emergency braking

Spring brakes are normally used to provide parking and emergency braking. During driving, air pressure holds the springs back; removing or losing that pressure allows the springs to apply the brakes. Normal service braking is controlled with the brake pedal rather than by routinely applying the spring brakes.

Source: Illinois CDL Study Guide — § 5.1.14, “Spring Brakes”

Question 3

In an air-brake system, what is a “wig wag”?

  1. A A mechanical arm that warns of low air pressure
  2. B A device that measures brake-lining wear
  3. C A switch that operates the brake lights
  4. D A lever used to drain the air tanks

Correct answer: A – A mechanical arm that warns of low air pressure

Illinois describes a wig wag as a low-air warning device that drops a mechanical arm into the driver's view when system pressure falls below 60 psi. An automatic version rises when pressure returns above 60 psi. A manual-reset version must be moved out of view by hand after adequate pressure is restored.

Source: Illinois CDL Study Guide — § 5.1.11, “Low Air Pressure Warning”

Question 4

Which description best identifies spring brakes?

  1. A Hydraulically operated wheel brakes
  2. B The normal service air brakes
  3. C Mechanically applied emergency and parking brakes
  4. D Brakes installed only on trailers

Correct answer: C – Mechanically applied emergency and parking brakes

Spring brakes are commonly used to meet parking- and emergency-brake needs. Air pressure holds the springs back while driving, and releasing that pressure allows the springs to apply the brakes mechanically. This design does not depend on stored air pressure remaining indefinitely while the vehicle is parked.

Source: Illinois CDL Study Guide — § 5.1.14, “Spring Brakes”

Question 5

The S-cam drum brake is the most common type of foundation brake. True or false?

  1. A True
  2. B False

Correct answer: A – True

S-cam drum brakes are the most common foundation brakes. Air pressure moves the push rod and slack adjuster, rotating the S-cam so the brake shoes press against the drum. Wedge and air-operated disc brakes are less common types.

Source: Illinois CDL Study Guide — § 5.1.8, “Foundation Brakes”

Question 6

At operating rpm, which pressure buildup indicates an acceptable dual air-brake system?

  1. A From 85 to 100 psi within three minutes
  2. B From 85 to 100 psi within 45 seconds
  3. C Compressor cutout at 75 psi
  4. D Safety-valve opening at 125 psi

Correct answer: B – From 85 to 100 psi within 45 seconds

Illinois uses a buildup from 85 to 100 psi within 45 seconds at operating rpm as the standard check for dual air systems. A slower buildup may allow pressure to fall too low during operation. Larger-than-minimum air tanks may require more time, so the manufacturer's specifications must also be checked.

Source: Illinois CDL Study Guide — § 5.3.3, “Check Rate of Air Pressure Buildup”

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