Montana CDL — Air Brakes Practice Test 5

1.A bus has lost its main air pressure and the spring brakes are on. The driver uses the spring-loaded control fed by a separate air tank to release them and move. Why does the manual say to plan that move carefully?

The separate tank refills only when the engine is switched offUsing the control disables the service brakes for the rest of the tripThe separate tank holds only enough air to release the brakes a few timesThe spring brakes will not reapply once they have been released this way

2.The manual says the low air pressure warning must come on before tank pressure falls below 55 psi. What alternative figure does it give for older vehicles?

20 to 45 psi80 to 85 psiOne half of the compressor governor's cutout pressureThe governor's cut-in pressure

3.A driver makes a habit of manually adjusting his truck's automatic slack adjusters every week. Besides hiding a mechanical problem, what does the manual say this routine is likely to cause?

Higher governor cut-out pressureFaster air pressure buildupA longer push rod stroke limitEarly wear of the adjuster itself

4.According to the manual, why can't air pressure alone be trusted to hold the emergency and parking brakes on?

Because the air can leak away over timeBecause air reacts more slowly than mechanical partsBecause air pressure would overheat the drums while parkedBecause air-held brakes never need to be adjusted

5.Before checking slack adjusters on s-cam brakes, the manual has you chock the wheels on level ground and then release the parking brakes. Why release them?

So that the air tanks drain while you workSo that the low air warning can be tested at the same timeSo that the brake drums cool fasterSo that the slack adjusters can be moved by hand

6.A driver wants a passenger endorsement and will drive a bus that has air brakes. Besides the test on Sections 2 and 4, what does the manual say this driver must also pass?

A knowledge test on Section 9, Hazardous MaterialsA knowledge test on Section 7, Doubles and TriplesNo other knowledge testA knowledge test on Section 5, Air Brakes

7.On a long grade your application pressure gauge shows you are using more and more pressure just to keep your speed steady. What does the manual tell you to do?

Slow down and shift to a lower gearSpeed up so more air flows over the drumsSwitch the front brake control to "slippery"Pull the parking brake knob to rest the service brakes

8.You have parked with the spring brakes applied. Why does the manual warn against pressing the brake pedal down now?

It would release the spring brakes and let the vehicle rollIt would trip the low air pressure warningIt would drain the separate tank used to release the spring brakesThe springs and the air pressure acting together could damage the brakes

9.On an icy road, the driver of a pre-1975 truck moves the front brake limiting valve control to "slippery." What does the manual say about that choice?

It is the required setting any time the pavement is slickIt doubles the air pressure sent to the front brakesIt shuts off the rear brakes so the front wheels can steerIt cuts stopping power; braking is unlikely to skid the front wheels even on ice, so the control belongs in "normal"

10.During the emergency brake test on the vehicle inspection test, you are fanning off air in a vehicle whose valves are not the pop-out kind. How does the manual say you will know the parking or emergency brakes have applied?

By listening for air discharging from the air systemBy watching for the ABS lamp to flashBy feeling the brake pedal go to the floorBy waiting until the gauge reads zero