Illinois CDL — Air Brakes Practice Test 9

1.What is the 'wig wag' device on some air brake vehicles?

A buzzer that sounds when the tanks are fullA gauge needle that flutters at cut-outA mechanical arm that drops into your view when pressure falls below 60 psiA warning lamp on the trailer's rear corner

2.How do you test the low air pressure warning during the final air brake check?

Rev the engine to full throttle and read the gaugeDrive at 5 mph and stab the brakes hardFan the pedal with the engine off and power on to lower pressure, and confirm the signal comes on before 60 psiDrain the tanks fully and listen for the buzzer

3.After the start-up bulb check, the ABS malfunction lamp stays lit. What does that most likely mean?

The tanks are fully chargedThe parking brake is engagedThe compressor has reached cut-outABS control may have been lost at one or more wheels

4.Why is needlessly pumping the brake pedal a bad habit in an air brake vehicle?

It overheats the compressor drive beltIt permanently warps the S-camsIt switches the system over to secondaryIt can bleed air out faster than the compressor rebuilds it, and low pressure disables the brakes

5.On some pre-1975 trucks, moving the front brake limiting control to the 'slippery' setting does what?

Cuts the normal front brake air pressure roughly in halfDoubles the pressure to the front brakesShuts off the rear brakes entirelyLocks the front wheels for extra grip

6.Which description matches the 'stab braking' emergency method?

Hold the brakes fully locked until you stopBrake all the way, release when the wheels lock, then reapply fully once they rollFeather the pedal lightly and steadilyUse only the parking brake control

7.You find you must keep increasing application pressure to hold a steady speed. What does this most likely indicate?

The brakes are fadingThe tanks are overfilledThe ABS has engagedThe governor is stuck at cut-in

8.With the engine off and the foot brake held down on a combination vehicle, air loss should not exceed how much in one minute?

About 4 psiAbout 10 psiAbout 20 psiAbout 40 psi

9.When checking a manual S-cam slack adjuster, about how much movement at the push-rod point suggests it needs adjustment?

Any movement whatsoeverMore than four inchesMore than roughly one inchExactly a half inch, no more

10.Why can you still apply the brakes several times even if the compressor quits?

The wheels generate braking air as they turnThe governor manufactures air on demandThe storage tanks hold a reserve of compressed airThe alcohol evaporator supplies backup pressure