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.
One additional thought: since I'm somewhere between cheap and frugal I might in your situation take the following approach to hedging my bets. If the corrosion is external as it appears and is limited in area I might have a good radiator shop close off the bad tubes as long as most of the cooling area remains, this is a judgement call. I would not replace the radiator until I was sure I had found the cause of the corrosion. I would probably do this even if I had to take it slow up some hills on a hot day until I knew for sure the problem was solved. I hate these problems with ambiguous causes.
Very good points Jon, especially about closing off some tubes. My '98 had corrosion at the bottom of the radiator and the fins were becoming detached on those tubes. I had the core replaced just before selling it. No idea how old the radiator was though.
(09-21-2016, 10:00 AM)ccjohnson Wrote: [ -> ]You might get a quote from a good radiator shop to recondition it. Should be substantially less costly than replacement with new one. Performance should be as good as a new one.
thanks, I will research that option.
(09-22-2016, 08:05 AM)77newell Wrote: [ -> ]One additional thought: since I'm somewhere between cheap and frugal I might in your situation take the following approach to hedging my bets. If the corrosion is external as it appears and is limited in area I might have a good radiator shop close off the bad tubes as long as most of the cooling area remains, this is a judgement call. I would not replace the radiator until I was sure I had found the cause of the corrosion. I would probably do this even if I had to take it slow up some hills on a hot day until I knew for sure the problem was solved. I hate these problems with ambiguous causes.
Jon, I like that approach, and my engine runs cool anyway so I doubt I would overheat on a hill. And if the engine runs in a low temp range I might just leave those tubes blocked off(expense on this issue is already out of hand). And as you state this provides me with the time to determine for sure what is going on; although I suspect it is electrolysis caused by 'stray' current (as a former boater I am all too aware of how much damage electrolysis can cause). Again, thanks for your input.
Just curious, is the location of the leaks and corrosion consistent across the replacement radiators, and if so, is that location consistent with the first failure?
I think Richard and Jon are on the correct track; I have been doing some reading and it appears that electrical current is responsible for a lot of radiator electrolysis failure (just never occurred to me, and also thought that it could not be the cause(so small a current!)-however 'expert' radiator sites list this as a major and substantial cause). Thanks everyone who responded; I am now on a mission to measure and track down electrical current and when verified rectify; then I intend to just have the tubes involved blocked off as I see no point in spending the money on yet another new radiator.
I believe the coolant level sensor is a 2 wire device that should be electrically isolated, ie; it should not be allowing electricity to escape into the radiator. Testing it would require removing it, energizing it and checking for voltage on the case.
If it is OK, then life gets more complicated. You then have to consider 2 possibilities; current flowing through steel framing parts and using the radiator as part of the path, or the engine is inadequately grounded and the coolant is carrying some charge that gets grounded through the radiator.
If the structure around the radiator isn't all welded together or otherwise electrically bonded, I would install grounding wires between the various parts and then to a secure grounding spot.
Regarding the engine grounding I would want to make sure there were good grounds on both the block and the head as these are where stray currents could access the coolant.
I'm not sure I'm being helpful here, but hopefullyam
Jon:
thanks for the info. I will be working on this issue shortly. Problems like this have a long life in tracking down the cause. And I suspect most rv repair facilities including DDA have little or experience with this happening (although I would hope the DDA shop has seen this before). My wife and I like the coach and have put money into repair/upgrades and new decor, so I really want to get this resolved and get back to the open road which we enjoy so much.
Again, thanks for your time and comments.