Iowa CDL — Air Brakes Practice Test 8

11.You take Iowa's air brake check in a truck towing a trailer that has no air brakes. Which leakage standard does the manual apply?

The same standard used for a single vehicleThe combination-vehicle standard, since any trailer makes it a combinationNone; the leakage test is skipped when the trailer lacks air brakesA stricter standard than either single or combination vehicles

12.Your truck has a modulating control valve handle on the dash. How does the distance you move the lever affect the spring brakes?

Any movement applies them fully, since the lever is only on or offMoving it farther releases the spring brakes moreThe lever only works the trailer brakes, never the spring brakesThe farther you move it, the harder the spring brakes apply

13.On Iowa's inspection test, you check the brake lines and hoses at the steering axle. According to the manual, what may a loss of air pressure in those lines cause?

The safety relief valve openingThe wheels locking upThe governor cutting out earlyFaster pressure buildup when the engine restarts

14.Four different rigs each lose 2.5 psi in one minute during their pre-trip air leakage checks, all with the engine off. Which rig should stay parked until the leak is found and fixed?

A tractor-trailer with the parking brake released and no brakes appliedA straight truck with the foot brake held fully downA straight truck with the parking brake released and no brakes appliedA tractor-trailer with the foot brake held fully down

15.When you inspect the air and electric lines between a tractor and trailer on Iowa's test, which check applies only to air brake systems?

Making sure the lines are not tangled or draggingListening for air leaksMaking sure the lines are free of cuts, cracks, and chafingMaking sure the lines are not pinched against vehicle parts

16.A driver figures that since his truck has working ABS, a couple of brakes running a little out of adjustment won't hurt his stops. Why is he wrong?

ABS automatically takes up the slack on any brake it controlsABS switches itself off whenever a brake drifts out of adjustmentABS works only on the steering axle, so rear brake adjustment is all that mattersABS is an add-on to the normal brakes and gives them no extra stopping power

17.Parked at a fuel stop with the engine running, you hear the safety relief valve on the first air tank let air out. How should you treat this?

As a fault in the system that a mechanic needs to repairAs normal venting each time the governor stops the compressorAs the automatic drain clearing water and oil from the tankAs the alcohol evaporator purging ice out of the valves

18.All four of these vehicles have air brakes. Which one was built before its antilock brake requirement took effect?

A truck tractor made in December 1997A converter dolly made in April 1998A semitrailer made in January 1998A bus made in June 1998

19.While you're driving, a mechanical arm suddenly swings down into your view. What has happened?

The governor has cut out the compressor at about 125 psiThe ABS has sensed a wheel that is about to lockThe safety relief valve has opened at about 150 psiThe air pressure in the system has dropped below 55 psi

20.You keep fanning off air after the low pressure warning test. On a straight truck with no trailer, what should pop out on its own once pressure falls to the manufacturer's setting?

The parking brake valve, setting the spring brakesBoth the tractor protection valve and the parking brake valveThe safety relief valve on the first air tankNothing; on single vehicles the spring brakes must be set by hand