# Free Iowa CDL Air Brakes Practice Test 2023

Do you need an Iowa Air Brakes endorsement or an L endorsement for your commercial driving license? The Iowa CDL Air Brake test has some differences from other endorsements because your license will receive a mark of restriction if you fail the test. So having good preparation before exam day is very necessary. To ensure that our questions are relevant, all of our CDL practice test packs are based on the Iowa CDL Manual. Each question has a detailed explanation for you to thoroughly learn the format and the topic. Don't be afraid of having a restriction on your license. Let’s try our Iowa CDL Practice Test to get ready to pass the Iowa CDL Air Brake Test now.

Our CDL practice tests:
Based on 2021 IA commercial driver's license manual
Perfect for first-time, renewal applicants
IA CDL Air Brakes Test format:
25 questions
80% passing score
List of questions
1.
Your truck or bus has a dual air brake system. If a low-pressure warning comes on for only one system, what should you do?
2.
Modern air brakes combine three different systems. They are the service, the parking, and the _____ brakes.
3.
On a long or steep downgrade, the foot brakes should be used:
4.
The 3 individual systems of the air brakes are the service brakes, emergency brake, and:
5.
Your truck has a dual air system and one of the systems loses its pressure. What will happen?
6.
With air brake vehicles, the parking brake should be used:
7.
When increased application pressure to maintain the same speed becomes necessary, you should ______.
8.
When stab braking if you re-apply the brakes before the wheels start rolling, __________.
9.
All of the following are factors in total stopping distance except:
10.
In a dual air brake system, the first system, supplying the rear brakes, is commonly known as the "primary" system, and the other as the:
11.
Pressing and releasing the brake pedal unnecessarily:
12.
Brake drums (or discs) must not have cracks longer than ____ the width of the friction area.
13.
When inspecting the air brake system, what particular item in the engine compartment should the driver pay specific attention to?
14.
Pushing the brake pedal down harder __________.
15.
In a dual air brake system, if the air pressure in one part of the system drops enough to set off the low air warning:
16.
How does the antilock brake system benefit the driver?
17.
If air supply drops when driving, the tractor protection valve ________.
18.
Brake drums or discs _______.
19.
Why should air tanks be drained completely?
20.
To avoid damaging the brakes, what should you never do while the spring brakes are applied?
21.
Vehicles without automatic air tank drains need to be checked manually to remove ________?
22.
In a dual air brake system, one system will typically control the rear brakes, and the other:
23.
Vehicles with ABS have malfunction lamps that are what color?
24.
The warning light and buzzer will come on when the air pressure in either system drops below what psi?
25.
What is the function of a safety valve?