Washington CDL — Air Brakes Practice Test 8

11.Which statement about ABS on an air brake vehicle is accurate?

It shortens your stopping distance in every situation.It replaces your normal service brakes entirely.It works continuously the whole time you brake.It is an addition to your normal brakes and only activates when the wheels are about to lock.

12.How can brakes that are out of adjustment lead to a loss of braking on a long hill?

They lock their wheels first and drag the vehicle sideways.They stop carrying their share, so the remaining brakes overheat and fade.They bleed air out of the tanks until the governor cuts in.They keep the spring brakes from ever applying.

13.What is the basic job of the air compressor on an air brake vehicle?

To bleed water and oil out of the reservoirs each night.To force air into the storage reservoirs that feed the brakes.To convert engine vacuum into hydraulic pressure for the wheels.To warn the driver when tank pressure has dropped too low.

14.The visible low-air-pressure warning must come on before tank pressure drops below what level?

60 psi.100 psi.125 psi.20 psi.

15.When should you avoid setting the parking brakes and use wheel chocks instead?

When the brakes are very hot from a steep grade, or very wet in freezing temperatures.Whenever the vehicle is loaded to its rated weight.Any time you park on level ground.Only when the alcohol evaporator is full.

16.When you press the pedal on an s-cam brake, what does the s-cam itself do?

It clamps a rotor between two caliper pads.It rotates and forces the brake shoes apart against the drum.It vents excess pressure back to the tanks.It draws the shoes away from the drum to release them.

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

It will drain the trailer air line.It disables the low-air warning.It recharges the springs incorrectly.The combined spring and air forces could damage the brakes.

18.In the applied-pressure leak test with the foot brake held down, a single vehicle should not lose more than how much in one minute?

Two psi.Four psi.One psi.Three psi.

19.Why do some buses have a separate air tank tied to a dual parking control valve?

So the spring brakes can be released briefly to move the vehicle in an emergency.So the compressor can be bypassed during inspections.So the trailer brakes can be charged independently.So the alcohol evaporator has its own air source.

20.What is the purpose of a modulating control valve for the spring brakes?

To drain the tanks gradually overnight.To keep the compressor from cutting out.To let you apply the spring brakes gradually if the service brakes fail.To raise the safety valve setting on grades.