Colorado CDL — Air Brakes Practice Test 6

1.Air pressure has fallen far enough that the spring brakes apply on their own. What hazard does that create for a lightly loaded truck or one on a slick road?

The air compressor will overheat and shut itself downThe wheels can lock and the vehicle may slide out of controlThe parking brake knob will push itself back inThe foot brakes will keep working at full strength

2.The governor stops the compressor from adding more air at about what pressure?

About 55 psiAbout 125 psi, known as the cut-out levelAbout 100 psiExactly 150 psi

3.What condition of the brake linings should cause you to reject the vehicle during inspection?

Linings that are lightly dustyLinings soaked with oil or grease, or worn dangerously thinLinings that are warm to the touchLinings that are a dark color

4.When testing the low pressure warning signal, before what pressure must the warning turn on?

Before pressure drops below 55 psiBefore pressure drops below 20 psiOnly after the spring brakes applyBefore pressure reaches 125 psi

5.In an air brake system, what does the air compressor do?

It pumps air into the storage tanks that supply the brakesIt warns the driver whenever tank pressure drops too lowIt converts stored air back into engine powerIt removes moisture and oil from the tanks automatically

6.Why are the air storage tanks important if the compressor suddenly quits working?

They cool the compressed air before it reaches the brakesThey automatically restart a failed compressorThey warn you the compressor has stoppedThey store enough air to apply the brakes several more times

7.If the low air pressure warning comes on and pressure keeps falling, why can a heavily loaded vehicle need a long distance to stop?

Because the service brakes get stronger under loadBecause the spring brakes do not work on all of the axlesBecause the compressor speeds up under loadBecause ABS shuts off when air is low

8.Before the air pressure in the tanks falls below what level must a low air pressure warning come on?

125 psi55 psi20 psi10 psi

9.Using the proper braking technique on a downgrade, when should you release the brakes during each application?

As soon as you first touch the pedalOnly after the vehicle comes to a full stopOnce speed drops to about five mph below your safe speedWhen speed climbs ten mph above your safe speed

10.What causes brakes to fade from excessive heat?

Overheating that reduces lining friction and expands the drumsToo much moisture drained from the tanksUsing the engine to help slow the vehicleRunning the compressor above cut-out pressure