Thread: Thoughts on 2012 dexcool in a 5.3l suburban

It's about time to change the coolant in my suburban. Typically I would flush out the dex and refill with green. They seem to have the plumbing more messed up on the new ones and I'm not sure I can get all the dex out with 1 shot. It only has 45K. So I could just drain and refresh with dex.

I heard the new dex is not as bad as the old but not sure.

It should I flush and not worry about some mixing?

Thanks for your thoughts.


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I did my 00 Silverado at 100K and it was about 8 years old. I'd service it with fresh Dex and be done.

Dex gets a bad rep when it really shouldn't. Most car manufacturers changed over to a nylon based gasket and had issue with them distorting. GM was no different. Early versions of Dex did sludge when exposed to air. Overall though our cooling systems should be closed.

If we look at the 3800 LIM gaskets we get quite a lesson in what happened. All nylon, they distort and GM decides to add metal rings by the bolts.
The metal ringed ones distort and GM decides to go with metal frame and the problem is solved.

Dex has a bad rap for no good reason. If you ever pull the factory plastic lower intake manifold gaskets out and see how they're all busted up and split, you'll know that wasn't caused by a chemical. Chemicals melt stuff, not crack and split stuff. That cracking and splitting is caused by heat. The new Fel-Pro steel-backed gaskets eliminate that issue.

Thanks for the thoughts. Yes dexcool's downfall is air and our GP's system is open to air through the overflow tank. That's why I prefer green in there. The 2012 suburban's overflow tank is pressurized so not open to air so I'm less concerned. Even though the miles are low I'm past the 5 years so I may just drain the system and refill with fresh dex that seems the easiest preventative step right now.


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Well I drained and filled my 2012 suburban today. Still not impressed with dex cool ! Took the overflow tank out to rinse it out and boy what a mess.



Dex crap coating the inside of the tank and the hoses coming from it.



Even though my suburban only had 45000 miles on it I'm convinced time and air are the killers of dex. The fluid itself that drained out seemed nice and reddish orange bit quite the layer of Scum on stuff.



I suspect air is somehow introduced into the overflow tank through this hole on the bottom.

Not sure how long I will leave this batch of dex in but next time I do it I need to order a new overflow tank and flush the system.

Weird thing is I threw my bottle of prestone flush in the overflow tank with hot water and let it sit and shook for 20 min and it did not even cut into the crud.

After discovering the mess I took the upper radiator hose off on the other side of the radiator to see if scum was in there and it appeared to not be as prevalent so hoping it is confined to areas near the overflow tank.