North Carolina CDL — Air Brakes Practice Test 8

1.When the low-air warning first lights up while driving, what should you do?

Keep going and pump the pedal to rebuild pressureCome to a controlled, safe stop immediately, before you lose the ability to brakeWait for the spring brakes to stop the vehicle automaticallyRelease the parking brake control to add air

2.Why is it important to drain the air storage tanks?

Water and oil collect inside and can harm the system, and the water may freeze in cold weatherDraining resets the governor's cut-in and cut-out settingsIt recharges the alcohol evaporator for winter drivingIt is the only way to release the parking brakes

3.The brake pedal in an air-brake vehicle, sometimes called the treadle or foot valve, controls braking how?

Each press sends the same fixed amount of air no matter how hard you pushPressing harder delivers more air pressure to the brakesIt only works once tank pressure climbs above 150 psiIt mechanically clamps the drums without using any air

4.What does the supply pressure gauge tell the driver?

How many miles remain before the tanks must be drainedHow hard the driver is pressing the brake pedalHow much air pressure is currently stored in the tanksWhether the ABS system is working

5.What happens if a major leak lets all the air out of the brake system?

The service brakes lock only the front wheelsNothing happens until you press the pedalThe compressor keeps the vehicle stopped on its ownThe springs apply the brakes

6.What is a 'wig wag' device?

A valve that limits air to the front brakes on iceA mechanical arm that drops into the driver's view when pressure falls below about 60 psiA second gauge that shows trailer tank pressureA lever used to apply the spring brakes gradually

7.If your tanks have manually operated drain valves rather than automatic ones, how often should you drain them?

Once a weekAt the end of each driving dayOnly when the low-air warning soundsAbout every 5,000 miles

8.What causes brakes to fade?

Draining the air tanks too oftenOverusing the service brakes instead of engine braking, which builds excessive heatFilling the alcohol evaporator in warm weatherSetting the parking brake while moving

9.If one circuit of a dual air brake system loses most of its pressure, what should you expect?

The other circuit shuts down as wellEither the front or rear brakes lose power, so stopping takes longerThe parking brakes release automaticallyBraking is completely unaffected

10.Which type of foundation brake is the most common on air-brake vehicles?

The S-cam drum brakeThe wedge brakeThe air-operated disc brakeThe band brake