Maryland CDL — Air Brakes Practice Test 3

1.What is brake lag, the extra delay that air brakes add to stopping?

The distance you coast before noticing a hazardThe short delay while air travels through the lines to the brakesThe time it takes the compressor to refill the tanksThe gap between the tractor and the trailer brakes

2.Where is the yellow ABS malfunction lamp located on a trailer?

In the center of the rear bumperOn the left side of the trailerOn the tractor's instrument panel onlyUnderneath the trailer near the axle

3.With the foot brake fully applied for one minute, what pressure loss is too much for a combination vehicle?

More than one psi in one minuteMore than two psi in one minuteMore than three psi in one minuteMore than four psi in one minute

4.If an air compressor is built with its own separate oil supply, what should you do before driving?

Drain all of the compressor's oil out firstDisconnect the compressor from the drive beltCheck the compressor's oil levelAdd alcohol to the compressor housing

5.You are hauling a trailer that has antilock brakes behind a tractor that does not, and the tractor begins to jackknife. What is the right response?

Press the pedal harder to force the tractor back into lineGrab a lower gear and hold steady pressure on the pedalPull the parking brake knob out to straighten the combinationBack off the brake pedal, where it is safe to do so, until you have the rig under control again

6.How do air brakes actually bring a heavy vehicle to a stop?

Compressed air presses the shoes or pads against the drum or rotorBrake fluid is pumped under pressure to each wheel cylinderEngine vacuum pulls the linings tight against the drumsAn electric motor spins the wheels backward to slow them

7.During the air leakage test on a single vehicle with the engine off and brakes released, what is the maximum acceptable pressure loss?

Up to 10 psi in one minuteLess than two psi in one minuteLess than six psi in one minuteAny loss under 20 psi in one minute

8.Which brake-related defect is described as the most common problem found during roadside inspections?

Brakes that are out of adjustmentCracked windshield glassUnderinflated spare tiresMissing mud flaps

9.On a dual air brake vehicle, how much pressure should the compressor build in both systems before you drive?

At least 55 psi in either systemAt least 150 psi in the primary system onlyA minimum of 100 psi in both the primary and secondary systemsExactly 20 psi in each system

10.What is physically going wrong inside a drum brake when too much heat makes the brakes fade?

The air lines soften and start bleeding pressure out of the chamberThe lining grips less and the drum swells, so the shoes reach farther and push with weaker forceThe slack adjuster tightens up and drags the shoes against the drumThe s-cam turns the wrong way and holds the shoes apart