Week of Jan, 5, 2009 Air Brake System

by Collin Barnette
(Visalia, CA)

Sorry for my absence these past few days things have been a little hectic for me. I will now try to bring you up to date on what's been happening at Truck Driving School.

As promised, I will first talk about the "Air Brakes Systems Check".

In California, that's where I am, You must say to the Examiner. "I will now preform my Air Bakes Systems Check", "For this I will need maximum air pressure". If your system is above the governor cut in, you use your pedal to loose some air.

Start the Truck and let the system build up to the maximum or governor cut out. Place the truck in gear, shut off the engine and release the clutch. Then you release the brakes.

Remember you are always demonstrating control of the truck. Your gauges will stabilize. Place firm steady pressure on the brakes and wait for your air gauges to stabilize again.

Then you will say that your gauges have stabilized and give the readings. You tell the examiner "I must loose no more than 4 PSI in one minute", "My minute begins now".

of course, this figure can vary depending on the truck and or trailer combination.

You hold the pedal for the minute.

"My minute has ended", then tell weather or not you have lost any pressure and how much. Give the readings of your gauges again. "This completes my Applied test".

"The next test I am going to preform is my Low Air Warning Test", " My low air warning must come on no lower than 55 PSI and I will let you know when this occurs". A few good steps on the brake pedal will use up plenty of air with the truck shut off.

Oh, if your key is not on you will not have a light so don't forget. "My low air warning has come on at____PSI". "This completes my low air warning test".

Set your brakes, the next tests will require you to start the truck and you want to maintain control.


"The next test I will preform is my governor cut in test", "My governor must cut in no higher than 130PSI and I will let you know when this occurs". Start the truck and run the engine until your air gauges have stabilized. Not at the sound of the pop off valve. Wait a few more seconds.

"My governor has cut in at ___PSI, I know this because my needles have stabilized". Give the readings of your air gauges. "This completes my governor cut out test". "The next test I will preform is my governor cut in test". "My governor must cut in at no lower than 85 PSI and I will let you know when this occurs".

Use the brake pedal to use up some air and then the throttle for ten seconds. Watch those gauges. Use some more air, back on the throttle. "My governor has cut in at ____PSI". Give the readings of your gauges. "I can tell this because my gauges are rising". "This completes my Governor Cut In Test".

"My last test will be my Parking Brake Test". Place the truck in gear and release the Emergency Brake. Slowly release the clutch until the truck strains against the brakes. "My Parking Brake is working, I know this because I can feel the truck tug against the brakes". "This completes my parking brake test and my air brakes system check".

You must perform this test with no errors. If not you will not go forward until you can.
This sounds like a lot but the information you are communicating to the examiner and verifying for yourself is that you have a solid understanding of what your brake systems are supposed to be doing and that you have positive control.

Practice, Practice and don't stop doing this just because the DMV examiner isn't setting over your shoulder.

The knowledge may save you from a catastrophe out there on the road.