Help tracking down air leak

Ok. Well it works fine.. but MAYBE leaking. I'm not 100% sure here. Thats my issue...

 

I think its leaking on the inner side I cant see. Thats a guess right now.

But riddle me this...Why does it ONLY leak when the tractor brakes are released??

 

No...but that one black 'switch' in the photo is a cruise control pressure switch. It is unique to Detroit Diesel.

That could be the cause of my leak AND the reason my cruise doesnt work SOME of the time...(I can set it and it doesn't hold).



Each of these are about $13. Not bad at least...

 

Thats the symptom I have had. Wont set at times or kicks out at times.
(Thats in another separate thread...) - Sometimes when it would kick out, we would hear a blast of air. (NOT the turbo winding down either).
The dealer told me I was nutz and that nothing cruise related runs on air. Hmm.....

Today I stopped at KW. Picked up 4 sensors. Both LOW PSI, brake switch and cruise switch. $72 I think was the total charge. I am going to replace all of them while I am in there. Maybe a waste of money but still cheaper than paying someone to work on it (before I loose my mind).

Since my air leak is not 'always' but 'most of the time' I am thinking it is one of these sensors. I would expect a hose that has a bad fitting to leak basically all the time.
I am changing the electrical connections on the cruise sensor to eyelets that will hold under the screw, instead of those "open hook electrical connector" things. Those sometimes spread out when you tighten down the fittings. - using eyelets will stop that.

Now, if something STILL leaks after all of this - then I dont know what else to do. The manifolds and hole-plugs are all tight.

 

Well if it is, it has passed all soapy water tests...even running my hand around the bottom of it..no air was to be felt and the sound is not coming from that valve (top or bottom is 100% quiet)....im sure its still possible, but I dont see how at this point.....