Massachusetts CDL — Air Brakes Practice Test 5

1.You have just pushed through deep standing water and your brakes are soaked. How does the manual say to get them working again?

Keep the vehicle in a low gear and press the pedal gently as you drive so heat dries the brakes outPull and push the parking-brake knob repeatedly until the water clearsOpen every tank drain valve and let the system blow itself dryCoast in neutral at highway speed so airflow dries the linings

2.On a vehicle that has a dual air system, what pressure must the compressor reach in each system before you set out?

55 psi100 psi85 psi150 psi

3.How can brakes that are out of adjustment lead to a complete loss of braking on a long grade?

They quit carrying their share, so the remaining brakes take the extra heat, fade, and leave too little stopping powerThey lock their wheels first, which actually shortens the stopThey force the governor to cut the compressor out earlyThey raise the pressure at which the spring brakes apply

4.With the system charged, the engine off, and the foot brake fully applied, the pressure on a combination vehicle should not fall more than how much in one minute?

2 psi3 psi4 psi6 psi

5.Which foundation brake is the most common on air-brake vehicles?

Air-operated disc brakesThe s-cam drum brakeWedge drum brakesHydraulic caliper brakes

6.Why can you still apply the brakes a few times after the compressor quits?

The storage tanks keep a reserve of compressed airThe pedal mechanically clamps the shoes without airThe alcohol evaporator makes backup pressureThe wig wag pumps air when the compressor quits

7.On newer air-brake vehicles, what does the parking-brake control look like and how do you set it?

A round blue knob you push in to applyA yellow, diamond-shaped knob you pull out to apply and push in to releaseA red octagon you turn a quarter turnA foot pedal left of the service brake

8.As soon as the low-air warning light and buzzer come on, what is the correct action?

Keep going until the spring brakes apply themselvesPump the pedal to build pressure back upStop the vehicle somewhere safe immediately, while you still have enough air to control brakingPull the parking-brake knob out while still moving

9.What is the role of the service brake system?

It applies and releases the brakes with the pedal during ordinary drivingIt holds the vehicle still after you park and walk awayIt stops the vehicle only when an air line rupturesIt feeds compressed air to the tires

10.When checking manual slack adjusters on s-cam brakes, about how much movement where the push rod attaches suggests they need adjustment?

Any movement at allMore than one half inchMore than three inchesMore than about one inch