# 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
Full answers + detailed explanations
Perfect for first-time, renewal applicants
IA CDL Air Brakes Test format:
25 questions
20 correct answers to pass
80% passing score
List of questions
1.
The safety valve discharges automatically at the pressure of:
2.
The driver must be able to see a low air pressure warning which comes on before pressure in the service air tanks fall below ____ psi.
3.
When is it OK to leave your truck unattended without applying the parking brakes and choking the wheels?
4.
A dual air brake system ________.
5.
Total stopping distance for air brakes is longer than that for hydraulic brakes due to ______ distance.
6.
The ____ shows how much pressure is in the air tanks.
7.
Brake fade is caused by:
8.
When the engine is off and the parking brake released, a single vehicle air loss rate should be less than ________ psi in one minute.
9.
When testing air leakage rates for single vehicles, initial loss rate should be less than:
10.
Some vehicles are equipped with a control allowing you to apply the spring brakes gradually, called a:
11.
If the spring brakes are on, when should you push the brake pedal?
12.
What must the air pressure be, at minimum, in both parts of a dual air brake system?
13.
If the low air pressure warning light comes on, you should:
14.
Besides heat, another cause of brake fade is:
15.
The parking brake should not be used when wet in freezing temperatures, or:
16.
The S-cam:
17.
Repeatedly partially increasing and pressing the brake pedal may result in:
18.
At minimum, a dual air system should build up to what psi in the primary and secondary systems?
19.
Which of the following helps the stop light switch work?
20.
The safety valve in the air compressor tank is set to open at _____.
21.
On large buses low pressure warning devices usually signal at ______.
22.
What brake system uses part of the service and parking brake systems to stop the vehicle in the event of a brake system failure?
23.
What is a wig wag ?
24.
A warning to drivers behind you that the air brakes have been applied is the:
25.
Manual air tank drains require: