Minnesota CDL — Air Brakes Practice Test 3

11.When checking manual slack adjusters, about how much movement suggests they need adjustment?

More than about one inch where the push rod attachesAny movement at allMore than about four inchesMore than half the length of the push rod

12.Using proper downgrade braking, once you are in a low gear, when do you release the brakes after applying them?

Only after coming to a complete stopAs soon as you feel any slowdown at allWhen your speed climbs back up to your safe speedAfter your speed drops to about five mph below your safe speed

13.Why can the brakes still be applied several times even if the compressor quits working?

The governor keeps the compressor spinning on engine powerThe alcohol evaporator releases stored pressureThe wig wag pumps backup air into the linesThe storage tanks hold a reserve of compressed air

14.If one half of a dual air system loses most of its pressure, what should you expect?

The other half automatically shuts off tooThe parking brakes will releaseNothing changes because the systems are identicalIt will take longer to stop, so stop safely and get it fixed

15.You are stopping a tractor-trailer on which every axle has a working antilock system. What braking method should you use?

Pump the pedal repeatedly so the computer has time to cycleReach for the trailer hand valve first and finish with the pedalStay off the service brakes entirely and let the engine slow the rigBrake the way you always have, applying only the force the stop calls for

16.How often must you drain air tanks that have manually operated drain valves?

Only when the low-air warning comes onOnce a weekAt the end of each day of drivingOnly before a long downhill grade

17.On the application pressure gauge, needing steadily more pressure to hold the same speed is a sign of what?

The tanks are overchargedThe brakes are fadingThe governor has cut outThe alcohol evaporator is empty

18.When testing the governor, at about what pressures should the compressor start and stop pumping?

Start at 55 psi, stop at 100 psiStart at 85 psi, stop at 120 psiStart at about 100 psi, stop between 120 and 140 psiStart at 120 psi, stop at 150 psi

19.What is the purpose of the electric heating device found on some automatic air tank drains?

To speed up how fast the compressor builds pressureTo keep the automatic drain from freezing in cold weatherTo warm the alcohol before it enters the air linesTo dry the brake linings after driving through water

20.Which way do you move the parking brake control knob to set and then release the parking brakes?

Pull it out to set them, then push it back in to release themPush it in to set them, then pull it out to release themRotate it clockwise to set them and counterclockwise to release themHold it down until the low-air warning clears, then let it spring back