Iowa CDL — Air Brakes Practice Test 9

11.Automatic slack adjusters are meant to keep brakes in adjustment, yet one of yours is past its legal pushrod stroke limit. Which explanation does the manual NOT offer for that?

A mechanical problem inside the adjusterA problem with the foundation brake parts connected to itAn adjuster that was installed incorrectlyAir tanks that were not drained at the end of the day

12.Two drivers take the same long downgrade at the same speed. One is in a proper low gear and brakes only now and then. The other stays in a higher gear and rides the service brakes most of the way. Whose brakes are more likely to fade, and why?

The first driver's, because a low gear makes the brakes work harder on every applicationThe second driver's, because leaning on the service brakes without engine braking builds too much heatNeither one's, since air brakes are built to absorb any amount of heat a downgrade producesBoth equally, because brake fade depends only on how heavy the load is, not on technique

13.During the engine-area fluid check on Iowa's inspection test, which fluid on the list applies only to vehicles with hydraulic brakes, not air brakes?

Brake fluidEngine oilCoolantPower steering fluid

14.In the final air brake check, your governor stops the compressor at about 130 psi rather than 125. What does the manual say about the exact cut-out point?

Any cut-out above 125 psi means the governor has to be replacedThe safety relief valve should be reset to open at 130 psi to matchThe 125 psi figure is approximate, so compare the result with the manufacturer's specificationsCut-out pressure only matters on single air systems built before 1975

15.In a truck with a dual air brake system, the low air light and buzzer come on. One gauge still reads 110 psi while the other is falling. What should you do?

Keep driving to your destination, since one system is still fully chargedStop right away in a safe place, park, and get the air brakes fixedPump the brake pedal to shift air from the full system into the low oneKeep driving, but make your stops with the parking brake control only

16.You're using controlled braking in an emergency in a truck without ABS, and the wheels lock. What does the manual tell you to do?

Release the brakes, then put them back on as soon as you canHold the pedal down so the locked wheels scrub off speedTurn the steering wheel sharply to break the wheels looseSet the parking brake so it takes over from the service brakes

17.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

18.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

19.On Iowa's inspection test, you check that the power unit's parking brake holds a combination vehicle. How should the trailer brakes be set during that check?

Released, so only the power unit's parking brake is holdingApplied, so the trailer helps hold the rigReleased, with your foot holding the service brake downIt does not matter, as long as the vehicle does not move

20.A heavily loaded truck loses its air to a leak, and the spring brakes come on. Why will it need a long distance to stop?

The spring brakes do not act on every axleSpring brakes only grip once the truck slows below 20 mphThe compressor pushes back against the springs until the engine is shut offThe ABS keeps releasing the spring brakes so the wheels stay turning