What is this Dexcool reservoir sludge/gel, and how do I get rid of it?

[Oro_O]

You might try this, its very effective. It comes in lesser quantities.

I might. I just worked on it a bit.

- Pulled the block drain plug (I did not before) - sludge on the end and threads.
- Pulled lower rad hose - clean except tiny bit near outlet hose on rad.

Seems to cling to metal (or the hard plastic ABS reservoir) and not the EPDM hoses.

I filled it again with water + 1/2 cup of TSP, which should solvate it, and drove it until the thermostat opened. I’ll drive it short distances to open the thermostat/get it hot the rest of today and see what drains out tomorrow am or late tonight, repeat that a few times.

Well this was an unexpected chore but also learning exercise, though not a disaster as far as I can tell at the moment.

 

[Oro_O]

OK, for you die-hard fans, I have an update. Yes it was definitively an air leak that caused the DexCool gelling/mud slime.

Good news: I now know why.

Bad news: I will get the chance over the next week to learn how to do a head gasket job on a GM 3400 “High Value” V6. Oh joy.

This car was LITERALLY driven from new by a little old lady (my mom), gently, until now, and maintained by the book (dealership + me). Yet here we are. Thank you GM.

That is one of those things, like a) learning to rebuild a GM 4L30E, b) perform a colonoscopy, c) tell your college roommate that his beloved Collie had just died, or d) pull small fragments of your own jaw bone out of your cheek,*** that I REALLY never wanted to do or even learn how to do, but was forced to do at the time. Oh well, I guess I will embrace the “suck” (do you see the joke I did there?). Also my parents are in the upper leagues of awesome so I will do what needs to be done.

*** - Do not ever misread the the Portuguese as a mild or even kind people. Nightlife in Lisbon can turn ugly, and fast.

 

[michaelluscher]

What causes it, per GM and Texaco, as I have read is air. Not mixing, but air in the system. DexCool apparently is HIGHLY susceptible to oxidative damage, and the silicates drop out of solution and form this brown, oily sludge

This video isn't terribly relevant to your particular vehicle, but some tidbits of Dexcool (and how it doesn't like contact with air)

 

[Oro_O]

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).