Iowa CDL — Air Brakes Practice Test 10

1.On Iowa's inspection test, you check the air lines between the power unit and an air-braked trailer. What does the manual say a low air condition can do to the trailer?

Set its spring brakes suddenly, which may cause a loss of controlRelease its brakes so it rolls freely behind the tractorTurn off only its marker and brake lightsRaise its landing gear automatically

2.What is the key difference between the controlled braking and stab braking methods for an emergency stop?

Controlled braking stays just short of locking the wheels; stab braking brakes fully and lets off whenever the wheels lockControlled braking relies on the parking brake; stab braking relies on the foot brakeControlled braking holds light, steady pressure; stab braking taps the pedal lightly and quicklyControlled braking is meant for hydraulic brakes; stab braking is only for vehicles with ABS

3.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

4.On the walk-around, the slack adjusters on two trucks each move about two inches at the push rod when you pull on them. One truck has manual slack adjusters and the other has automatic ones. What does the manual point you toward?

Adjust both by hand, since any slack adjuster moving more than about an inch simply needs taking upAdjust the manual one or have it adjusted, and get the automatic one to a repair shop soon because its stroke signals a mechanical faultLeave both alone, since slack adjusters only need attention if the service brake test pulls to one sideSend the manual one to a repair shop, and hand-adjust the automatic one back within its legal limit before leaving

5.You drive a tractor-trailer with ABS on both the tractor and the trailer. How much braking force does the manual tell you to use when you slow down?

Just enough to stop safely and keep control, easing off if either unit starts to get out of lineA full, hard application every time, so the ABS can handle all of the wheel control for youLight, rapid pumps of the pedal so the ABS computer has a chance to reset between themMore force than you would use in a rig without ABS, since ABS always shortens the stop

6.You passed the air brakes knowledge test. In which skills-test vehicle would you avoid both the L and the Z air brake restrictions?

A truck with hydraulic brakesA truck whose brakes work fully on airA truck with air-over-hydraulic brakesAny of these, as long as you pass the skills test

7.Your truck's air compressor is driven by gears off the engine rather than by a belt. How does that change the air brake check in the engine compartment step?

You check the compressor gears for tightness in place of a beltThe drive belt check doesn't apply, since it is only for belt-driven compressorsYou drain the air tanks during that step insteadNothing changes; you still check a compressor belt for condition and tightness

8.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

9.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

10.Which statement about the air compressor does NOT match the manual?

It is turned by the engine, using gears or a v-beltIt pulls its air out of the brake chambers at each wheelIt may be cooled by air or by the engine's cooling systemIt may use engine oil or have an oil supply of its own