Well, now I am seeing red:
Outside temps almost up to 80 degrees today, and I put the Jeep to a bit of work. Didn't turn out so well with the new radiator.
:banghead:
The cause is pretty simple: An unsupported O-ring seal:
You can see the coolant spraying out of it at 6:00 in the picture, 9:00 on the fitting if you were in the engine bay looking at it.
I had reservations about the fitting at the time I installed the radiator, but hoped it wouldn't matter. Well, false hope is still hope.
In order for an O-ring to do its job well it needs to be supported on all four sides (looking at a cross section of the seal). In this case the O-ring only has support on three sides. The unsupported side allows pressure to escape.
There would be two intelligent design solutions here: One would be to machine the fittings such that the seal is entirely within the female side of the fitting so that all four sides are supported. The other would be to use a solid material, like perhaps delrin or nylon. Something malleable enough to form a seal, but strong enough not to be able to blow out.
Of course this problem shows up on a Friday afternoon on a holiday weekend. I will have to wait until next week to see what sort of answer I get from Cold Case.