Air Brake Pressurize Time?

dj2109 · 04-29-2021, 10:36 PM

Hey guys I totally drained my air tanks (dont ask why)

how long does it take to pressurize from empty? im afraid there’s a leak....

thanks

rossvtaylor · 04-29-2021, 10:44 PM

It's never a problem to drain them...so I won't ask! The fill time depends upon the bus. If you have air bags, it will take longer than a bus with springs. It's pretty normal for a bus to build pressure to about 60 psi, then "stall out" for a bit while air then fills the aux tank. The time to fill all this depends upon the size of the system (tanks and air bags), and the engine RPMs.

We've got some buses that air from empty to full in 6-7 minutes, but a couple have air starters and a huge starter tank...and those can take almost 15 minutes at idle.

dj2109 · 04-29-2021, 10:49 PM

dang thanks for the info

its been 20-30 and they wont pressurize...

dj2109 · 04-29-2021, 10:49 PM

i know nothing about busses or diesel mechanics so im really unsure what to do... any tips?

dj2109 · 04-29-2021, 10:53 PM

we were supposed to leave tonight but now we cant lol

rossvtaylor · 04-29-2021, 11:01 PM

Is there any chance that one of the tank drains is stuck open? You would hear it, I think, but if you drained the tanks and left a valve open or one of them stuck open that could certainly be a problem. Also, are you somewhere where it's freezing cold right now? If you get water in the valves or lines and it freezes, that can prevent pressure build.

o1marc · 04-29-2021, 11:03 PM

Mine only take a few minutes at most, if it's been 20, you definitely have a leak.

dj2109 · 04-29-2021, 11:11 PM

nothing is leaking, ive checked everywhere, my hands are now black

o1marc · 04-29-2021, 11:17 PM

Quote:

Originally Posted by dj2109

nothing is leaking, ive checked everywhere, my hands are now black

Then it's likely a compressor issue, bigger deal than a leak.

dj2109 · 04-29-2021, 11:34 PM

im in california. not cold! lol

dj2109 · 04-29-2021, 11:35 PM

does this affect transmission? it wont move when in gear

o1marc · 04-29-2021, 11:38 PM

Quote:

Originally Posted by dj2109

does this affect transmission? it wont move when in gear

Air brake buses will not go in gear unless pressured up. Brakes won't release without pressure, that bus aint moving unless you release the brakes from underneath, or fix the issue.

Airbrake procedures is one of the very first thing you should learm about before driving a bus.

dj2109 · 04-29-2021, 11:49 PM

ok so im revving it in neutral and it sbuilding. good?

dj2109 · 04-29-2021, 11:51 PM

i cant get it past about 20 psi...

o1marc · 04-29-2021, 11:58 PM

Quote:

Originally Posted by dj2109

i cant get it past about 20 psi...

It won't release until it's over 100. it'll shut off at around 120.

Memorize this:

https://cdltesttruck.com/class-a-air-brake-test

dj2109 · 04-30-2021, 12:22 AM

hey guys im really struggling. im not sure how that link applies to me. brakes wont build past 20 psi. does anyone have the ocams razor solution? im really begging here

o1marc · 04-30-2021, 12:35 AM

Quote:

Originally Posted by dj2109

hey guys im really struggling. im not sure how that link applies to me. brakes wont build past 20 psi. does anyone have the ocams razor solution? im really begging here

It applies to you and you don't know it. You would not pass a CDL test with out knowing this. While we don't have to be licensed to know how to drive one of these, you should not drive one if you are not familiar with the basics of air brake operation.

You have a leak or bad pump.run it for a bit, then shut it off and listen carefully around the compressor or air lines for sounds of leaking.

Go to the UserCP and fill out your profile with your location, it'll help with your issues.

o1marc · 04-30-2021, 12:37 AM

Quote:

Originally Posted by dj2109

hey guys im really struggling. im not sure how that link applies to me. brakes wont build past 20 psi. does anyone have the ocams razor solution? im really begging here

It applies to you and you don't know it. You would not pass a CDL test with out knowing this. While we don't have to be licensed to know how to drive one of these, you should not drive one if you are not familiar with the basics of air brake operation.

You have a leak or bad pump.run it for a bit, then shut it off and listen carefully around the compressor or air lines for sounds of leaking.

Go to the UserCP and fill out your profile with your location and bus info, it'll help with your issues.

dj2109 · 04-30-2021, 12:55 AM

thanks i drove tanks in the infantry so im ok with big trucks

i have a small leak.

what is average psi for releasing air brakes?

thanks for help

rossvtaylor · 04-30-2021, 06:25 AM

Quote:

Originally Posted by dj2109

i have a small leak.

what is average psi for releasing air brakes?

thanks for help

Typically, you'll have enough pressure to release the spring (parking) brake at about 60 psi.

Where is the small leak you mention?

And...you said you drained the tanks and not to ask...but this may be relevant. If the system was working before and isn't now, with no changes, then something broke or froze. But if you worked on something or made changes, it would be helpful to know what you did/changed so we can better help. So, what were you working on when you drained the tanks?

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