[FLYNAVY30]

the sacrificial zinc in the radiator looked brand new after 2 years, so I would guess electrolysis is not the culprit here.

One of the guys on the ProTouring forum pointed out that the Entropy radiators have the top plate welded on, thus tying the end tanks, cap, and core together. Because the core will expand at a different rate than the solid top cap with heat, he suggested you can end up braking the welds in the core. It does make sense as the core was leaking from both top corners.

I went ahead and ordered a cheap, chinese aluminum radiator that doesnt have a top plate. We'll see how it holds up.