Over the last year, the print head has sprung a pinhole leak in the machined cooling channels.

In my quest for making it ultra lite, I previously moved the water cooling channels to the bottom of the head as it made sense.  So there is an aluminum cover plate held on by nothing other than activated Lock-tite. I think the leaking problem is the result of the hot-end radiantly heating the cover plate and eventually degrading the Lock-tite.  Or I could have just overheated it.  Either way, it leaks a tiny bit.

Interestingly enough this isn't much of a problem to the point that I haven't bothered to fix it.

The cooling system is basically sealed and the print head is at the lowest point. When I fill it with water it leaks for a little while until the pressure at the print head equalizes with air pressure, drawing a little vacuum on the rest of the system. Then it stops leaking, and is good for another 3 months.  Barometric pressure and temperature variances cause a drip or two or it would be stable. 

The previous version of the head was a couple grams heavier due to requiring more AL, but the cover plate was sandwiched between the main body and the mixing motor then and so the seal was inherently stable.  It also didn't get radiantly heated there, and it would take some massive overheating to break down the Lock-tite in that location.  

I think I'll move it back.