Minnesota CDL — Air Brakes Practice Test 9

1.How often must you drain air tanks that have manually operated drain valves?

Only when the low-air warning comes onOnce a weekAt the end of each day of drivingOnly before a long downhill grade

2.On a long, steep downgrade, the service brakes should be used in what way?

As the only means of controlling speedHeld down continuously the entire way downOnly as a supplement to the braking effect of the engineNot at all once you are in a low gear

3.Where is the ABS malfunction lamp located on a truck tractor or bus?

On the left rear corner of the frameOn the instrument panel in the cabInside the first air tankNext to the parking brake knob only

4.Which way do you move the parking brake control knob to set and then release the parking brakes?

Pull it out to set them, then push it back in to release themPush it in to set them, then pull it out to release themRotate it clockwise to set them and counterclockwise to release themHold it down until the low-air warning clears, then let it spring back

5.Why should you avoid pressing the brake pedal while the spring brakes are already applied?

It could release air needed for the next stopIt resets the ABS malfunction lampIt slowly drains the secondary tankThe combined force of the springs and air pressure could damage the brakes

6.Why is it important to completely drain the water that collects in the air tanks?

In cold weather the water can freeze and cause the brakes to failWater raises the governor cut-out pressure too highWater makes the low-air warning buzzer sound constantlyWater disables the automatic slack adjusters

7.What most commonly causes air brakes to fade?

Draining the tanks too oftenOverusing the service brakes instead of the engine to slow down, which builds excessive heatRefilling the alcohol evaporator too frequentlySetting the parking brake while moving

8.How are the spring brakes kept released while you drive normally?

The compressor mechanically locks them openThe modulating valve holds them outAir pressure holds the powerful springs backThe governor keeps them from engaging

9.How should you test the service brakes during the final air brake check?

Roll forward slowly at about five mph and apply the brakes firmly, watching for pulling or delayApply the brakes hard at highway speedHold the pedal down for a full minute while parkedPull the trailer hand valve while stopped

10.Why shouldn't you set the parking brakes when the brakes are very wet in freezing temperatures?

The water raises tank pressure dangerouslyThe wig wag will not resetThe brakes could freeze so the vehicle cannot moveThe alcohol evaporator will overflow