[77newell]

The pattern of these failures suggests that one of two things is going on; a problem developed that caused the very first failure to ruin the original radiator in its last two years and that problem has yet to be addressed, or the original radiator died of natural causes (though it seems to be to be a bit young for that) and when its replacement was installed something was different and has remained the same with each subsequent replacement. In the former case you would be looking for something like a ground connection that got corroded which then sent current though the radiator seeking ground AND was not touched in any of the later radiator replacements. In the latter case you are looking in detail at what was touched during the radiator exchanges to find something just a bit off such as grounding a sensor to the radiator itself rather than to the chassis.

I'm really suspecting that something was changed in the original radiator exchange and the later repairs just copied what was there and repeated the cause of the failure. In any case, taking your time and putting a finger on every part and following it from end to end. Also be aware that coolant probably has enough ions in it to carry charges from the engine (with a bad ground) to the radiator (this would lead to the failures in the first case noted above).

This message was written in stream of consciousness by a guy running a fever so take it for what you find of value.