Missouri CDL — Air Brakes Practice Test 1

1.Why should you avoid pressing the foot brake while the spring brakes are already applied?

It drains the tanks instantlyIt disables the ABS warning lampThe combined force of the springs and air pressure could damage the brakesIt makes the governor cut in early

2.What best describes a dual air brake system?

One system driven by two compressorsA system that switches between air and hydraulicA single system with two governors and one tankTwo separate air brake systems operated by a single set of controls

3.On newer vehicles, how do you set the parking (spring) brakes?

Push the round blue knob inPull the yellow, diamond-shaped knob outwardHold the brake pedal down firmlyTurn the ignition key to the lock position

4.What happens when you press the brake pedal (treadle valve) down harder?

The compressor cuts outThe parking brakes releaseA greater amount of air pressure reaches the brakesThe safety valve opens

5.What does it indicate if the safety valve lets air escape?

The tanks are properly chargedSomething is wrong and a mechanic should fix itThe governor has reached its cut-in pointThe alcohol evaporator has run dry

6.What is the purpose of an alcohol evaporator in some air brake systems?

It lubricates the s-cam and slack adjustersIt raises tank pressure above the governor settingIt lowers the chance of ice forming in the valves during cold weatherIt filters oil out of the compressed air

7.How large a crack in a brake drum is unacceptable during inspection?

Any hairline mark on the outer surfaceA crack shorter than one inchOnly a crack that goes fully throughA crack running more than half the width of the friction area

8.Why do the brakes still work for several applications after the compressor stops running?

The wheels store energy that runs the brakesEach brake chamber holds its own backup canisterThe governor makes air without the compressorThe storage tanks keep a reserve of compressed air on hand

9.How do spring brakes hold the vehicle when the air pressure is lost?

A backup compressor keeps them chargedHydraulic pressure takes over automaticallyPowerful springs, held off by air while driving, clamp the brakes once the air is goneA parking pawl locks the transmission

10.What does a supply pressure gauge tell the driver?

How much air pressure is stored in the tanksHow hard the brakes are being appliedThe temperature of the brake drumsWhether the parking brake is set