This video isn't terribly relevant to your particular vehicle, but some tidbits of Dexcool (and how it doesn't like contact with air)
Actually that’s an awesome link (watched it). I have been trying to dig up online the. older docs on this and not successful. In the last few days I read a TON of comments on serious GM forums about GM and Texaco (dexcool original maker) comments and suggestions about this issue - in this engine and others. I tried to find the old TSBs and could not find live links to post, but found a lot of dead links. Good link/good job you did.
But see my just-made post above, this turned out to be the sub-standard gaskets they put in the 3400 engines and not the DexCool per se. In fact, had I swapped in an AMAM fluid years ago, I might NOT have caught this head gasket issue until it got a lot worse. Of course, it being DexCool also means I have sludge in the head and water passages, which I would not otherwise have. (I found evidence of that pulling the block drain bolt if I did not already mention that). Grrrr….
These EXACT 3400s have a unique designator as LNJ engines and went into ONLY Pontiac Torrents and 1st Gen Equinox - they were sub-contracted in China (yes), and went into ONLY the Torrent and Equinox, vs other 3400s that went everywhere else - Malibus, Impalas, etc. I don’t know if non-Chinese GM 3400s of the period have the same gasket issues, but when I look on Torrent/Equinox forum(s), this is really common. I did not know this before. Again, a collective “high-five” to GM and it’s love of Chinese production. (jk)
(Side addition: Michael, I appreciate your comments and posts. Not just for their content but as I also used to be an NYC resident and had to pretty much fight/pay through the nose to be a car-owner/enthusiast there. I like your sig line and have enjoyed it a while but not openly acknowledged that).