Minnesota CDL — Air Brakes Practice Test 2

1.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

2.How does an air brake system turn on the brake lights to warn drivers behind you?

An electric switch operated by air pressure closes when you brakeThe wig wag completes the light circuitThe governor signals the brake lamps directlyThe slack adjuster trips a mechanical switch

3.What is the purpose of a modulating control valve?

To apply the spring brakes gradually if the service brakes failTo cut front brake pressure in half on slippery roadsTo keep the compressor from over-pressurizing the tanksTo automatically drain the tanks each day

4.If the ABS on your vehicle malfunctions, what happens to your braking?

The spring brakes take over completelyYou lose all braking until it is repairedOnly the front brakes will workYou still have your normal brakes and should get the system serviced soon

5.Why can a heavily loaded vehicle take a long distance to stop once the spring brakes come on?

The spring brakes do not act on all of the axlesThe service brakes lock every wheel at onceThe load raises the governor cut-out pressureThe ABS shuts the brakes off under heavy loads

6.With the engine off and the parking brake released, the air pressure loss on a single vehicle should be no more than how much per minute?

4 psi6 psi3 psi2 psi

7.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

8.Compared with hydraulic brakes, air brakes add an extra delay called brake lag. Why does it happen?

The driver reacts more slowly in a large vehicleIt takes time for the air to travel through the lines to the brakesThe spring brakes must release firstThe governor must reach cut-out pressure first

9.During a routine stop in a truck with a manual transmission, when should the clutch go in?

The instant your foot touches the brake pedalNot until engine rpm has fallen close to idleAt roughly half of the speed you started braking fromOnly after the vehicle has been sitting still for a few seconds

10.Before driving a vehicle with a dual air system, you should wait until the compressor builds at least how much pressure in both systems?

55 psi100 psi120 psi150 psi