Tennessee CDL — Air Brakes Practice Test 3

1.What does the service brake system do?

It applies and releases the brakes as you work the brake pedal during normal drivingIt holds the vehicle still after you have shut down the engineIt stops the vehicle only when the main air supply failsIt cools the brake drums between hard stops

2.What is the job of the air compressor in an air brake system?

It drains moisture out of the storage tanksIt pumps air into the storage tanks so pressure is availableIt measures how much pressure is being applied to the brakesIt releases the spring brakes when you park

3.When using stab braking, why must you wait before re-applying the brakes after releasing them?

The tanks need time to refill above cut-out pressureThe stop lights need a moment to resetThe governor must cut in before you can brake againThe wheels can take up to a second to start rolling, and you must let them

4.What can happen if you press and release the brake pedal more than necessary?

The governor is forced to raise the cut-out pressureThe safety valve is prevented from openingThe air is used up faster than the compressor can rebuild itThe stop lights stop working

5.As soon as the low-pressure warning light and its buzzer come on, what is the correct action?

Keep driving until the spring brakes apply by themselvesBring the vehicle to a safe stop while you can still control the brakesPump the pedal quickly to rebuild pressureIgnore it until the gauge reads zero

6.What happens to a brake drum if the brakes are used so hard and so long that they overheat?

Too much heat can cause the brakes to stop workingThe brakes grip more strongly than normalThe drum automatically switches to the spring brakesThe governor lowers the tank pressure to compensate

7.On a long, steep downgrade, the braking effect of the service brakes should be treated as what?

The only thing you need to control speedOnly a supplement to the engine's braking effectA replacement for gearing downSomething to avoid using entirely on hills

8.What is the main job of an antilock braking system (ABS)?

It shortens the vehicle's stopping distance on every surfaceIt keeps the wheels from locking up during hard brakingIt replaces the need for a parking brakeIt raises the governor cut-out pressure automatically

9.While driving, the low-pressure warning suddenly comes on. What is your safest move?

Speed up to reach your destination before pressure runs outPump the brakes hard to keep pressure upStop and safely park as soon as possibleSet the parking brake while still moving fast

10.At roughly what pressure does the governor cut out and stop the compressor from pumping?

About 55 psiAbout 85 psiAbout 100 psiAbout 125 psi