Air Pressure Drop?

[dreamchasers]

What is a reasonable amount of air pressure drop during a 24 hour period on the main and aux air gauges on the dash? I am trying to 'tighten up' my air system.

Thanks,

Hector

[Steve Bennett]

We have had coaches that will stay up for 30 days plus with 0 air loss. Most will loose a couple of pounds per day on the aux system, but very little on the brake primary & secondary tanks. The colder the ambient air temperature, the quicker the air loss will typically be do to the contraction of the fittings. If your coach has an auxiliary air compressor, we feel it should not need to run more than once a day in normal climate.

[Joe Cannarozzi]

Hector this is a great question. Steve beat me to a responce but looks like we agree to a great degree.

DOT allows up to but not more than a 20psi drop in 10 minutes. That is with the brakes released. IMO that is ridiculous and bordering on unsafe and I am pretty confident no one here is anywhere near that bad.

So what you are asking is slightly different and want to know an acceptable amount of pressure drop with the parking brakes on.

IMO we are going for no loss at all.For perspective, I think if you can keep the aux air compressor to cycling once a day (if not using any pnewmatic accessories that would skew the loss levels) you are probably about average compared to the rest of the group.

Our bus was pitiful when we got it and would completely bleed off overnight.
I got it to the point that it would take a week until the suspension dumped. I know of other issues but do not have the doe to correct them. When I do I expect to see at minimum 100lbs indefinitely, at least that is what I strive for.

This is one of those issues for me. I have driven truck my whole life and was completely comfortable with reasonable or slight loss of pressure overnight. However since joining POG and being influenced by the likes of Jon that is no longer the case. There is no reason why given a reasonable amount of time we can not get these campers air tight or darn close to it.

So how about it Hector what kind of loss are we talking about here, Hmmmmmmmmmmm?

[dreamchasers]

Hector this is a great question. Steve beat me to a responce but looks like we agree to a great degree.

DOT allows up to but not more than a 20psi drop in 10 minutes. That is with the brakes released. IMO that is ridiculous and bordering on unsafe and I am pretty confident no one here is anywhere near that bad.

So what you are asking is slightly different and want to know an acceptable amount of pressure drop with the parking brakes on.

IMO we are going for no loss at all.For perspective, I think if you can keep the aux air compressor to cycling once a day (if not using any pnewmatic accessories that would skew the loss levels) you are probably about average compared to the rest of the group.

Our bus was pitiful when we got it and would completely bleed off overnight.
I got it to the point that it would take a week until the suspension dumped. I know of other issues but do not have the doe to correct them. When I do I expect to see at minimum 100lbs indefinitely, at least that is what I strive for.

This is one of those issues for me. I have driven truck my whole life and was completely comfortable with reasonable or slight loss of pressure overnight. However since joining POG and being influenced by the likes of Jon that is no longer the case. There is no reason why given a reasonable amount of time we can not get these campers air tight or darn close to it.

So how about it Hector what kind of loss are we talking about here, Hmmmmmmmmmmm?

I am definitely leaking, but I am aggressively tightening thing up.

I believe I have a leak on one of the many braking components located under the coach. Here's my reasoning. After rebuilding the Bendix AD-9 Air Dryer, I started the coach to build pressure. After the 125 psi control spitting of the air dryer, I let the coach sit all night and the next morning, still 125 psi on the main air, Hurray!!. Not so fast, today while replacing and testing other components for leaks, I pumped the brake pedal a few times to consume air and build pressure back to the max. Now I notice, I am leaking again. I will test some of the braking components tomorrow.

I predict when I go out to the coach in the am, I will have lost 50 psi in 12 hours. When I pump the brake pedal, I can hear air discharging when the pedal is released. I am sure one or more of the exhaust ports are leaking.

What do you recommend on the troubleshooting the braking components? Any magical ideas or things to avoid.

On the suspension side, I have corrected several very minor leaks and it is looking good (cracked fitting on the new air bag Prevost installed). I am using a home made pneumatic tester for checking leaking suspension components. It works great!

I also replaced the check valve in the main air tank and the check valve in the aux air tank. I am working my way through the braking system.

Hector

[Joe Cannarozzi]

It is normal for air to exhaust as you release your foot from the pedal. If you are holding the brake pedal down steady and you hear air leaking THAT is bad.

For those who missed this procedure before it is definitely worth repeating.

Testing air pressure and looking for leaks as a standard pre-trip check. If you want to be sure you are safe you should be doing this every time you start a day.

First:
Build up air till the air dryer goes off and the compressor stops building pressure, with the parking brakes on. Wait 10 minutes and record the drop.

If you have a loss here it is going to be aux. air or possibly service air too.

Next:
Now first release the parking brakes pump the brake pedal to get the pressure down far enough to get the compressor pumping air and again build up to 120. Wait 10 minutes and again record the drop but this time you have the parking brakes off.. (The DOT allows up to but not more than 20psi drop in 10 min.)

If an additional drop is observed from the initial test you have an emergency air leak. ( probably a maxi or a line going to it)

Finally:
again with parking brake released and air built up to 120 step on the brake pedal and hold. Turn the bus off and open a window to help you listen along with watching the gauges.

If you hear air leaking but only when you are applying brake pressure it is Service air. (IMO anything heard during this test is unacceptable)

In conclusion the easiest way to completely rid yourself of pressure loss is to first get it to hold air with the parking brake on. When you get to there then release the parking brake and again get it to hold.

I can't tell you how many times I have got to the end of a search confident I have finally found all the leaks only to come out the next day and see pressure loss, go over things again and find more. This project is a lesson in perseverance and one worth doing for sure.

[phorner]

Joe,

I like your attitude about zero pressure loss!!

Can't wait 'till you get your hands on our bus....

[lewpopp]

Hey Joe,

You are short on "doe"? Instead of using "doe", try using Lewbucks or DOUGH. If that doesn't work, use a buck or a fawn. Good ole Lew, trying not to miss a chance.

[Orren Zook]

Hey Joe,

You are short on "doe"? Instead of using "doe", try using Lewbucks or DOUGH. If that doesn't work, use a buck or a fawn. Good ole Lew, trying not to miss a chance.

I'm sure it was a Freudian Slip - hunting season has arrived in the midwest

[dalej]

Now I notice, I am leaking again. I will test some of the braking components tomorrow._Hector


When your coach is sitting in the park position there is no air going into any of the brake lines or chambers. There is air pressure from the brake tanks sitting at the park brake valve and the foot brake control valve waiting to be used.

[truk4u]

No air leaks.... You guys are dreaming!