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The air brakes endorsement applies to applicants who wish to drive a vehicle with air brakes in Class A, B, or C CDL. To drive a vehicle with air brakes, you must pass the air brake component of the Illinois CDL knowledge test. The IL CDL air brakes test consists of 25 questions, and you'll need at least 20 correct answers to pass (80%). The test covers the information found in the air brakes section of the Illinois CDL Manual. Take this IL CDL practice test now to prepare for the actual air brakes test!
1. If air pressure does not build up fast enough:
the pressure may drop too low during driving.
you should put the parking brake on and gently pull against it in a low gear.
you may be forced to turn off the engine and release the parking brake.
you should turn the electrical power on and step on and off the brake pedal.
2. The supply pressure gauges tell you how much air pressure:
is in the air brakes.
is in the air tanks.
you are applying to the brakes.
is going to the brake chambers.
3. If the low air pressure warning light comes on, you should:
stop immediately.
set the parking brake.
continue to drive normally.
call for help.
4. Which of the following is not a braking system on a truck?
Service brake
Steering brake
Emergency brake
Parking brake
5. Hydroplaning is more likely if:
the road is wet.
tire pressure is low.
tire tread is worn.
All of the above.
6. The trailer hand valve should:
be used in driving.
never be used for parking.
never be used to test the trailer brakes.
All of the above.
7. Before driving a vehicle with a dual air system, the air compressor should build up a minimumĀ of _____ pressure in both the primary and secondary systems.
10 psi
50 psi
100 psi
75 psi
8. When is it safe to leave your vehicle unattended without applying the parking brakes or chocking the wheels?
When the tank pressure falls to the "cut-in" pressure.
Only while you are taking a rest break.
When you are conducting your pre-trip inspection.
9. Under a pressurized system, the radiator cap:
should never be hot.
should never be removed until the system has cooled.
should be removed when the coolant is hot.
should always be cool.
10. Parking brakes are:
required on all vehicles.
not required on trailers.
not required on commercial vehicles with air brakes.
not required on buses.
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IL CDL Air Brakes Test

Number of questions: 25
Correct answers to pass:20
Passing score:80%
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