Iowa CDL — Air Brakes Practice Test 2

1.Your straight truck has ABS on all axles, but its yellow ABS lamp has stayed lit all day. A car stops suddenly ahead and you must brake hard. Which approach fits the manual?

Stand on the pedal and hold it, since full application is allowed on a truck with ABS on all axlesStop with the parking brake control alone, since the service brakes are tied to the failed ABSUse controlled or stab braking, since the regular brakes still work but the wheels can now lockPump the pedal lightly until the lamp goes out, and only then brake hard

2.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

3.Your truck has automatic air tank drains and an alcohol evaporator. During a cold snap, which daily task does the manual still give you?

Check the alcohol container and top it up as neededOpen each drain valve by hand at the end of the dayRun the engine at a fast idle until the safety valve opensBleed the tanks down to 55 psi to push out moisture

4.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

5.Most of the final air brake check is done with the vehicle standing still. Which part of it has you drive the vehicle forward?

The air leakage rate testThe low pressure warning signal testThe check that the spring brakes set on their ownThe service brake test at about 5 mph

6.You usually drive a medium truck with hydraulic brakes, but today you're in an air-braked truck at the same speed. Even if you react just as quickly, how should this change the room you leave ahead?

Leave the same room, because air brakes work the instant you touch the pedalLeave less room, because air brakes stop a truck faster than hydraulic brakesLeave more room, because air brakes need half a second or more to start working after you press the pedalLeave more room only on wet roads, because brake lag disappears on dry pavement

7.On Iowa's inspection test, you start up a combination vehicle whose trailer has ABS. What should the trailer's ABS light at the rear on the driver's side do?

Stay lit as long as the engine runsCome on, then go offStay dark the entire timeFlash until the trailer parking brake is released

8.During the parking brake test, you set the parking brake and pull gently against it in low gear, and the truck creeps forward. Which brake problem does the manual link to weak spring brakes?

An air tank that wasn't drained the night beforeAn alcohol evaporator that is running lowBrakes that are out of adjustmentA front brake limiting valve left in the normal position

9.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

10.The low air warning has just come on, and the needle keeps dropping. How long can you count on making a controlled stop with the brake pedal?

Until the needle reaches zero, since the springs take over graduallyOnly while enough air is left in the tanks to work the service brakesFor as long as the engine keeps runningFor about ten more brake applications, however low the pressure gets