Well, I found the air leaks at both air tanks and its ironic they are both leaking from the same brass 90 degree air fittings. (See photos)
It looks like a brass elbow and nut designed to retain the air line and there is only one like it on each tank.
I'm going to try and get the part number off Freightliner's website and see if it is actually two separate pieces....the elbow and retention nut/shark bite fitting.
The real problem is accessibility to each one to switch them out as they sit up high on the tanks.
With the coach running at high idle, the air dryer is purging every 15 minutes exactly.
Thoughts?