[Richard]

Tony,

Building on Steve Bare’s suggestion, it is logical that since the behavior follows the change in air dryer that the change is responsible. But, that may or may not be the case. Make yourself a leak down tester and plumb it just after the air dryer. That first step will allow you to isolate the air dryer install from the rest of the coach.

And what a way to get to know all the different plumbing fittings!

[Tfrazier]

Well its been a few days and I "think" I made some progress. I found 5 air leaks so far. One that is somewhat embarrassing, since I was so adamant that I had fully tested all of the connections from the air dryer install. And I swear that I did check them, but..... I missed a leak on the fitting at the delivery port. It wasn't noticeable from the front side of the connection, but when crawled around and looked at the backside, there was a whole bunch of big old bubbles. Just took a small turn of the wrench to tighten it up a bit. No more bubbles.
   

The second air leak was at the body of the valve that controls the generator access compartment. Replaced it today.
   

I already knew about the 3rd leak (stair cover valve). I changed out the spool on that one today and, holy cow, the stair cover works great now. This should hopefully eliminate the air leak. 

The 4th one was at a push-to-connect "T" that controls the basement freezer slide. Changed it out with a compression "T".

The 5th leak was at the unloader port of the governor.  Installed a new governor with all new fittings. 

Hopefully all of these fixes will help eliminate or at least minimize my air woes.

Thanks to everyone who chimed in on this thread. What started out as a pretty simple question about my old air dryer turned into a great learning experience for me. I appreciate all of the help.

[Tf175]

Glad you found the leaks , also learned about your air system . Your report will help others as well. 
Small leaks add up to one large total leak . I think I had 16% leak (maybe more) when I first tested with Snap On cylinder leak tester . Eliminated most of the small leaks , still haven't achieved zero . If I had time I would replumb the whole thing , make it as accessible as possible. One day maybe .
Chris

[Richard]

I hear you Chris, some of us have the fantasy of installing an air manifold system similar to the water manifold, where you can isolate many of the feed lines to different components.

[Tfrazier]

Update. Went over to the coach today, hopeful that I had cured my air leak ills. Unfortunately, there is still an air leak/s somewhere on the supply side. The brake side was at 60 but the supply side was at 0. I fired her up and it took about 45 seconds for the supply side to equalize with the break side and right a 4.5 minutes to climb up to 125 and purge. I believe I have checked most possibilities top side so the next step is to crib it up and crawl under.

[Richard]

Tony,

Just out of curiosity, if you allow the aux compressor to air up the coach, how long before the pressure leaks down enough for the aux to kick back on?

[Tfrazier]

Good morning Richard,
We took the coach to Aiken State Park this weekend for our preseason shakedown. Thought it would be a good time to try your experiment. The process went as follows:
Arrived at the camp ground Friday at 6:00 pm.the coach air was at 110. The site was level so I didn’t have to do anything with leveling. I started monitoring the gauges and by 8:30 the air was at 100. At 10:00 it was 85. At 7:00 am it was at 50 and seemed to hold steady there until around noon. During this period, the aux compressor never came on. At this point I exhausted the remainder of the air out of the system. During this process the aux compressor came on as soon as the pressure dropped below 50.
I shut the Aux compressor off and let all of the air deplete. Once down to 0, I turned the compressor back on. It took 12.5 minutes for the Coach to air up to 110 and then the aux compressor shut off. I started monitoring the air loss again and saw similar results as described above. I am now 17 hou Facebook rs in and the air is at 50 and the Aux compressor has yet to come on. Other than the fact that I have an obvious leak(s), any ideas on what I need to be checking? Thanks

[Tfrazier]

Update. Shortly after my last post, the alt compressor kicked on as the air dropped below 50. It took only about 5.5 minutes to get to 100. 30 minutes after that, we were ready to leave the site.  I fired the engine and it took about 2 minutes to hit 125 and purge.

[Tf175]

I had a leak at a hose fitting going to one of the suspension exhaust valves ( electric over air solenoid ) . That leak was always present , whereas your leak seems to be intermittent . I'm guessing here , but you might have a look at any solenoid that exhausts air . Your coach probably has the "six pack " valving , which should operate as my separate valves do . I can run my engine , get everything aired up , etc , supply and brake will be at 120 psi . In a few hours supply will usually be at or near zero , brake still at 100 or above . If coach is driven for several hours , the supply pressure will stay up for 2 or 3 days ( not at full pressure , but won't leak all the way down ) . It seems that this must be a valve somewhere that likes the effects of operation . Search continues ..
I also had leaking PPV ( pressure protection valve ) . This valve prioritizes air for the brakes , it's importance goes without saying .. It was not easy to access as I have to work from the ground !
As Richard says , isolate sections of the air system . Taken as a whole the system can appear bewildering , but when subsections are considered it minimizes the complexity . 
Chris

[Richard]

Tony,

You may be in the land of diminishing returns. Air comp cycling every three or four hours isnt bad, ot perfect but not bad. You are now looking for small leaks that only bubbles are going to show. Try using a sponge to bubble up the soapy water, and paint it the fittings with the foam. Learned that trick from steve denton