New Hampshire CDL — Air Brakes Practice Test 10

1.On older vehicles, the manual ties the low air warning to the compressor governor instead of to a fixed 55 psi. If such a vehicle's governor cuts out at 120 psi, when must the visible warning come on?

Before tank pressure falls below 60 psiBefore tank pressure falls below 30 psiBefore tank pressure falls below 45 psiBefore tank pressure falls below 100 psi

2.Driver A's CDL carries the L restriction and Driver B's carries the Z restriction. Going by the manual's definitions, which of them may operate a commercial vehicle with air over hydraulic brakes?

Driver B onlyDriver A onlyBoth driversNeither driver

3.Section 5 covers brakes that are too hot or too wet to set the parking brakes on. Which pairing of condition and remedy matches the manual?

Very hot brakes: set the parking brakes to hold the heat in. Wet brakes: drain the air tanksVery hot brakes: let them cool first. Wet brakes: drive in a low gear with light brake pressure until they heat up and dryVery hot brakes: pump the pedal rapidly. Wet brakes: set the parking brakes at onceVery hot brakes: work the parking knob in and out. Wet brakes: top up the alcohol evaporator

4.A drum brake stops the vehicle by pressing its shoes and linings outward on the drum. Besides slowing the vehicle, what does the manual say the resulting friction creates?

HeatExtra air pressure in the tanksMoisture in the brake chambersSlack in the push rods

5.Wedge brakes and S-cam brakes use different mechanisms. What does the manual's description show they have in common?

Both force brake shoes against the inside of a brake drumBoth use a power screw to clamp a rotorBoth rely on a caliper with lining padsBoth are self-adjusting on every vehicle

6.Several faults described in the Air Brakes section are handed to a mechanic or a repair facility. Which of these tasks does the manual say you must do yourself?

Draining manually operated air tanks once each day of driving is overFixing the fault when the safety relief valve releases airCorrecting a brake whose automatic slack adjuster is out of adjustmentRebuilding a governor that will not cut in or cut out

7.The safety relief valve is usually set to open at a fixed pressure. Using the manual's usual numbers, about how far above the governor's cut-out level is that?

About 5 psiAbout 25 psiAbout 50 psiAbout 95 psi

8.Step 3 of the seven-step inspection in Section 2 has you look at the gauges once the engine is running. What does it say about the air pressure gauge?

It should hold steady at 55 psi while the engine idlesIt should climb from 50 psi to 90 psi in no more than 3 minutes, and you go on building to governor cut-outIt should reach 150 psi before you release the parking brakeIt should drop 3 psi each minute until the engine warms up

9.In the manual's list of air brake parts, what are "foundation brakes"?

The spring brakes that hold a parked vehicleThe first air tank the compressor fillsThe half of a dual system that serves the rear axleThe brakes used at each wheel, most commonly S-cam drum brakes

10.Several times and durations appear in the Air Brakes section. Which pairing matches the manual?

One minute: how long you time the pressure drop in an air leakage test45 seconds: how long air takes to reach the brakes after you press the pedalThree minutes: how long each brake application lasts on a long downgradeOne second: how long a dual system takes to build from 85 to 100 psi