Another update. I fired up the other board in the unit and I am now hashing at about 1.3TH total and my hottest chip is 66C. The fans are barely running and the errors are well within range. I'm calling this a win. If the unit runs stable overnight I will move it to a more permanent location and let it eat.

I think what happens is the coolant in the system degrades and little bits of solids hinder the pump performance. I initially drained the system into a cup and there flakes of solids in there. Small ones but solids just the same. We will see how much temps change after the ethylene glycol. I also expect cooling performance to improve after the thermal paste has time to burn in. I have already seen significant improvement in just this short time.