Air tank pressures unbalanced and Parking break question

You were wrong, they build pressure unevenly. Tanks are filling. Did it build pressure and hold? I bet it did. My truck is the same, even with a blown air compressor.

 

That is normal. At least on every truck I have owned in the past 30 years, 7 in total, maybe 8, I forget. If I am wrong, I guess I have owned some messed up trucks. I am not a mechanic or certified to adjust my own brakes, but I have the tools to do it and have. And I have stayed in a Holiday Inn Express.

 

Read the book, hell I don't know. If you are below 20 psi on the brakes they are useless. I don't get anal on this stuff, and am not a mechanic or a DOT cop. I know when my brakes are not working, and have done some wild stuff with no brakes and broken airlines.

Right now, replacing my blown air compressor, she was fine if you just read the gauges, but I knew my brake system was not right as there were other signs. You are getting into the weeds here, you need to speak with a mechanic that knows the technical side of things. What you are experiencing here is quite normal in my book. As long as it loads air in what, one minute or there about from the buzzer going off you are good.

Not knocking your question, it is valid. Just kind of annoyed that you turned down that perfectly working truck to do your job. I have had drivers, and you brought back memories. LOL!

 

IF the truck fails the alarm requirement at 60 psi or lower do not drive it. It should kick in that protection valve for the tractor. I don't know the equivalent for a class B straight truck, but the result should still be the same when those yellow and red buttons pop. Your spring brakes then take over and apply.

Ive done some driving with trucks that were not that good with airpressure and have experienced losses that really should have put that tractor (And did...) into the shop in actual trucking. I recall one situation coming off 695 onto 83 south (Jones Falls Expway baltimore) ramp the air gauge would bleed from everything 120 on down to 40 or so as I slowed the rig for the ramp speed.

The problem was traced to the rubber shield between the service side and the spring side in the braking chamber having corroded and eaten through due to no air dryer on that tractor. Thus no draining of tanks each night leads to bad things that got into those brakes and started eating through. All of that was fixed soon enough.

Another time I had a tractor that failed the compressor when it broke during dinner at Doswell. Came back to a 18 wheeler that aint going no where with no air either. The resulting situation was then a really seriously epic story told elsewhere in my postings. It's better she died at dinner rather than 70 mph on 95 in middle of DC during rush.

You are doing what I think you are supposed to do prior to driving a truck. Keep it up. Usually when it breaks it will tell you then. Not out on the road hopefully.

 

Alarm should kick on by 60, trailer should exhaust shortly after that. Yellow button might not pop out until 20 psi left in most of the trucks I have driven. The difference in tanks isn’t so much important as the pressure loss when doing a pressure drop test with full brakes application for one minute, then it’s 2 psi and 3 psi if I am not mistaken.

I would have applied 90 psi to the truck and trailer and checked the stroke all the way around, and also see the pressure loss over a minute. Then you would know if it was satisfactory. Most DOT only want to hear the buzzer, see the warning lights, and hear the trailer pop off under 60 psi.