Not to drudge up any old, worn out debates, but the information I get about this is conflicting, to say the least. Even experienced mechanics can't seem to agree on this.

The Monte I just got came with the green stuff in it, and it actually looks pretty clean. I'm not overheating or anything, but I do want to replace the radiator and other cooling components due to damaged fins and rust on the outside. The question is: what do I fill it with after? One mechanic says that Chevy "got away" from using Dex because of gasket issues. Another says to immediately flush the green stuff out and get Dex.

So.... HELP!

 

I have flushed both of my montes using the regular green stuff and the Dex a few times each. I cleaned everything out to the best of my ability, flushing and rinsing for a few hours, driving, then repeat. I got all of the red stuff out as I could until I couldn't see any hints of it after a few days of driving, and every single time I used Dex it gummed up after a few days. I wouldn't use it.

 

I vote green!

Dex turns acidic after a while and rots gaskets like your guy said. Stuff also gums up from the slightest contamination. Head gasket leak, uim leak, lim leak..

 

IMO if its already got green, I'd probably just keep with that. Won't have to worry about being 100% perfect on your flush after replacing your components. No doubt the longer change intervals of dex would be nicer, but given its an older used car, its not like you've got 200k + left in it anyways.

I'm normally pro dexcool as I've got a ton of problem free miles with it across numerous GM vehicles, I'm just not a big fan of flip flopping between incompatible coolants.

If the bent fins are the bigger of the two concerns, they do make picks for straightening them out.

 

I go universal yellow after a chemical flush then 3 fresh water flushes. Dexcool is good if maintained but universal is pretty well mix and forget.

 

Sigh, this argument is so stupid. If Dex-cool was so bad, why does GM continue to use it? Literally most, if not all, problems associated with it virtually disappeared in the middle 00's (the whole Dexcool lawsuit debacle around that time, not-withstanding). The culprit was ****ty gaskets and vehicle neglect. Plus, it's a OAT coolant, which is what numerous other manufacturers (mostly foreign) are using too. If you don't fix a coolant leak or change the coolant at regular intervals (5 years/ 150k miles), yes it will "go bad", just like any other fluid in the vehicle.