Mississippi CDL — Air Brakes Practice Test 2

11.Which list puts these air system pressure points in order from LOWEST to HIGHEST, using the typical values in the manual?

Low air warning, governor cut-in, governor cut-out, safety valve openingGovernor cut-in, low air warning, safety valve opening, governor cut-outLow air warning, governor cut-out, governor cut-in, safety valve openingSafety valve opening, governor cut-out, governor cut-in, low air warning

12.Some pre-1975 trucks carry a front brake limiting valve worked from the cab. What was it meant to do, and what is the catch?

It was meant to reduce front-wheel skids on slick roads, but it actually reduces stopping powerIt was meant to cool the front brakes, but it wears out the liningsIt was meant to add front braking on ice, but it locks the rear wheelsIt was meant to replace ABS, but it works only above 55 mph

13.A parked truck slowly loses all its air overnight through a small leak. Why does its parking brake keep holding?

The governor locks the wheels when pressure dropsThe safety valve traps enough air to keep the brakes onIts spring brakes are applied by mechanical spring force, which does not depend on airThe ABS holds the brakes until the engine restarts

14.Which sequence matches the manual's normal stop in an air-braked truck with a manual transmission?

Clutch in first, then press the pedal hard, then shift to neutralPress the pedal and ease off as needed, clutch in once rpm nears idle, then pick a starting gear when stoppedPress the pedal hard, pull the parking brake knob, then clutch inShift to neutral, coast, then brake only in the last few feet

15.On some older air-braked vehicles, the visible low air warning is not tied to 55 psi. What is it based on instead?

The safety valve's opening pressureThe governor's cut-in pressureA fixed 80 to 85 psiOne half of the compressor governor's cut-out pressure

16.Which statement about automatic air tank drains is accurate?

They push out water and oil on their own, and some can also be drained by handThey still have to be opened by hand at the end of every dayThey cannot be fitted with heaters for cold weatherThey remove water but leave the compressor oil in the tank

17.A brake fitted with an automatic slack adjuster shows a pushrod stroke past the legal limit. What does this generally indicate?

Normal wear that a quick hand adjustment will fix for goodA mechanical problem in the adjuster or related brake parts, or a poor installationLow air in the secondary systemAir tanks that were overfilled

18.On a long downgrade in the right low gear, your 'safe' speed is 50 mph. You just braked down to about 45 mph and let off. When do you brake again?

Right away, to get down to 40 mphWhen your speed climbs back up to 50 mphOnly if you reach 60 mphNot again; hold 45 mph using the engine alone

19.You park after driving through slush, the brakes are soaked, and the temperature is below freezing. Why might setting the parking brakes be a mistake?

They will release by themselves as they dryThey could freeze so the vehicle cannot moveWet parking brakes drain the air tanksThe ABS lamp will stay on

20.In an s-cam brake, air entering the brake chamber pushes the rod out. Which part does the rod move next, twisting the brake camshaft?

The governorThe slack adjusterThe brake drumThe wheel speed sensor