Illinois CDL — Air Brakes Practice Test 5

1.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

2.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

3.On a typical air-brake vehicle, a visible low-air warning must appear before pressure drops below what level?

About 100 psiAbout 60 psiAbout 80 psiAbout 45 psi

4.What tends to gather at the bottom of the air tanks, making draining necessary?

Brake fluid and coolantAlcohol and antifreezeFine metal shavingsWater and compressor oil

5.While you are driving normally, what keeps the strong springs of the spring brakes from applying the brakes?

A mechanical latch on the camshaftAir pressure holding the springs backVacuum from the engine intakeTension in the slack adjusters

6.On a system with an alcohol evaporator but no automatic drains, what must still be done each cold-weather day?

Swap out the evaporator cartridgeReadjust the governorBleed the trailer service lineDrain the tanks to remove water and oil

7.How does ABS change a vehicle's normal braking ability?

It cuts normal braking power roughly in halfIt replaces the service brakes completelyIt neither adds to nor reduces normal braking and only acts when wheels are about to lockIt permanently doubles braking force

8.Drum brakes slow the vehicle through friction and heat. What can excessive heat do to them?

Recharge the air tanksApply the brakes automaticallySwitch braking to the secondary systemCause the brakes to stop working

9.What is a modulating control valve used for?

Draining the tanks automaticallyWarning the driver of low pressureApplying the spring brakes gradually if the service brakes failLimiting air pressure to the front brakes

10.Why should you avoid stepping on the brake pedal while the spring brakes are already set?

The combined spring and air forces could damage the brakesIt will silently release the parking brakesIt empties the trailer air tankIt forces the safety valve to open