[Brad Townsend]

So my air system has a leak even when I run the engine it fills up quick but after shutting the engine off the gauges will show empty in less than a day.
Not sure if the brakes are on as the brake gage shows empty. I have used a sniffer to check everything I can think of to no avail.
Any suggestions?

[RussWhite]

Brad, just to be clear, are you saying that the three gauges one for primary brake pressure one for secondary brake pressure and one for auxiliary air pressure all go to zero?

If that's the case, there is no single point of failure that I can think of that would produce that result . I think it would require both a failure of a check valve or check valves as well as a leak .

That's a whole lot there to lose in a day. I'm sure your sniffer can find it, but you have to be sniffing in all the right places .

[ccjohnson]

Sounds like a check valve problem to me. And, maybe check the drier discharge for leakage. Also might be possible to be bleeding back out through compressor if check valve is failing somewhere in the system. The fact that it airs up quickly seems to indicate check valve issue to me more than just a leakage problem.

[Brad Townsend]

I only have 2 gauges Brake and Supply. Would be nice if it is only a check valve. have checked around the 110 volt compressor and found nothing.
A bit windy out here in the desert currently to use the sniffer but will be at it again when wind goes away.

CCj, do you mean the 110 volt compressor or the engine compressor?

[77newell]

I would think there have to be a couple leaks, one in each of your brake systems (front brakes, rear brakes) for the symptoms you describe to occur. Air comes from the compressor into the "supply" tank, also sometimes known as the "wet" tank. Air then goes through separate lines and check valves into the two brake tanks. The rationale for this arrangement is that a problem in one brake tank should not effect the other tank. However, a leak in either tank will also drain the "supply" tank. The only place where the two brake systems are involved with a single component is at the foot valve, otherwise they are completely separate. With the brake pedal released you should detect no air venting from the back side vent on the foot valve. If there is any other internal problem with the foot valve it would gradually apply brakes and you would have noticed that.

The source most likely to cause leaks with the fewest components would be the tank drain valves. If they are the one automatic ones, I've had problems with those. Not bad problems, just annoying ones. Check if air is venting from these drains.

[rheavn]

" I have used a sniffer to check everything I can think of to no avail.  Any suggestions?"

Organize your search.  Break your air system into sections.  Use a leak down tool to find where you have leaks & where you don't.  Search for leaks in a similar method as you would an electrical problem.  Find where you have a leak, split the system in half and see which half, or if both halves have leaks.  

I just went through the same problem you have and my system now loses less than 1 pound an hour.

Might want to review these two threads.

http://newellgurus.com/showthread.php?tid=2690
http://newellgurus.com/showthread.php?tid=2697

[rheavn]

Here is one more thread to review

http://newellgurus.com/showthread.php?tid=2705

[Richard]

In my way of seeing it, if both the brake system and the supply system are leaking down then the massive leak has to be upstream. So Clints suggestion of looking at the air drier blowoff, check valve, and system between the engine air compressor and the first wet tank is logical

[Brad Townsend]

yikes this is getting pretty involved. Another thing I noticed is I think I have those automatic bleeder valves as i used to hear them bleed off occasionally but don't her them but of course after the air drains out I wouldn't I guess those are what you mean Jon. Good thing to check out. My 110 volt compressor won't catch up with the leak showing it to be pretty big, only with the engine will it fill quickly but then leak out quickly. Guess I have my work cut out.
Thanks guys. Wish some of you techies were close by.
Currently we are wintering just outside Yuma az. Boondocking.

[ccjohnson]

I was thinking engine compressor.  On the 2 times we have had a problem with the 110 compressor having long & often,  the leak that was causing most of the problem was the air shift module in the transmission.  Not a real major issue to fix.  Newell rebuilt it once & then Stewart & Stevenson put in a new on for us while they were resolving some issues I had with the engine repair job they did.  You could here air "bubbling" when you had your head in the engine compartment when it was very quiet with the coach inside the garage.  The S&S guy did the replacement at our home  in less than half an hr once he had the part in hand.  Both times the repair had the 110 compressor go from running 8-10 minutes every 20-30 minutes to only 2-3 minutes every 3-4 hrs.  Sorry I did not think about this on my first post.