Hello all, so I have a 2001 blazer 4.3liter. I'm going to flush the cooling system tomorrow. I know the owners manual says to use DEX-COOL but, i have heard nothing good about the stuff. I was thinking of completely flushing the system and using the regular green antifreeze/coolant. Does anyone have any advice on this topic? Please and thank you.

 

Have you tried searching the site with the search engine up above? Type in Dexcool and you'll see alot of opinions.

 

Yeah, lots of talk about dex cool and converting to conventional green. Captain hook talked me out of it a few years ago lol

 

There were problems with Dexcool in the early days of its formulation; something about when running the cooling system with much air in it would result in a precipitate forming. Also a precipitate would form if Dexcool was mixed with the traditional green stuff. This later issue has been remedied too for the most part.

When I replaced my coolant I did a complete flush and then refilled with Prestone Dexcool. Unless you have soft water at your garden hose, be sure to use distilled water. I flushed my cooling system about 5 times with distilled water and then drained off as much as I could and refilled with the correct amount of 100% Dexcool adding any remaining to the expansion tank.

 

Basically, Dex-Cool is designed to work with the aluminum in the engine and is fine if properly maintained. GM is even still using it for this reason. It just doesn't tolerate neglect or air in the cooling system very well. Personally I still run Dex-Cool and just keep up with the service intervals; it's really not all that hard.

When Dex-Cool was new, some shops didn't have it and either just added water which diluted the corrosion protection or added conventional green ethylene glycol antifreeze which reacted with the Organic Acid Technology in Dex-Cool to form a gritty sludge. Neither of these was really GM's fault. Some of the earliest '90s models also had manifold gaskets that didn't play well with the OAT either; this WAS GM's fault, but was quickly corrected and most/all of those gaskets have long since been replaced by now.

Dex-Cool doesn't tolerate neglect or air in the system well. Since it was advertised as "long life" Most People just ran it indefinitely without changing the coolant and/or just drained the radiator instead of thoroughly flushing the block; but when GM said 5 years or 150,000 miles though they weren't kidding. Most People also didn't test/change the radiator cap like it says to right on it, which can let air into the system and lead to problems. Most People also tended to ignore it as long as possible when they got a weeping water pump or gurgling heater core too. Dex-Cool acquired a bad reputation because Most People are idiots and blamed Dex-Cool when they got a problem that actually stemmed from neglect. But if you're not an idiot like Most People, you'll be in much better shape.

If this all sounds too scary and you want to switch to green, just be sure to COMPLETELY flush the system when doing so. They do not mix well together at all.

I've always used distilled water too, but as I was looking through the manual for something else the other night I saw that it just says, "clean drinkable water." Unless living in a place that I know has very hard water, I think I'll just use tap water from now on at least for the first flush or two, and maybe distilled for the final fill. If nothing else, I doubt the commercially packaged prediluted 50/50 stuff uses distilled water either.

The service manual also says you're supposed to crush two of these cooling system seal tabs into the reservoir, but I've never done that and I doubt it's ever been done in my truck since the factory in the 19 years I've owned it.

EDIT: and according to the MSDS, those tablets are more than 50% ginger. Not even kidding. Maybe I'll go add a couple pinches from my spice rack to the reservoir.

 

Mixing coolants way back at the beginning of Dexcool could cause some issues, but a few years in it simply reduced the service interval to the shortest interval of the two which is something that most people never paid attention to anyway. What most commonly occurred when coolants were mixed is that air was not properly removed from the system. Air in the system is what caused the issue of gritty sludge contamination. OAT coolants are much less prone to wetting (clinging of the liquid to the surface) which improves their heat transfer capability, but also reduces their ability to provide corrosion protection when an air pocket exists. Most common coolants now are this way as everyone is trying to do more with less.

The gasket troubles on GM's vehicles was due to the use of nylon as a gasket carrier material which was a glaringly stupid material to use on anything that is near water. Nylon becomes brittle & swells in the presence of water. There are nylon blends that can be more water resistant and these blends are used now in the redesigned "stock" replacement gasket sets, but they still will not have the service life of the old paper gaskets which is why there are upgraded aftermarket gasket sets with metal frames.

 

Very interesting! Thanks for correction on the details. Technically correct is the best kind of correct! Completely agree too that neglect and/or air in the system were the bigger culprits.

Just to pick a very minor point, some people had conventional antifreeze or straight water added to their Dex-Cool unwittingly by oil change shops etc. and then continued to drive it up to or beyond the stated 5-year service interval without understanding the implications. Dex-Cool wound up getting improperly blamed for issues that resulted from inadvertently over-extending the service interval that way. As I remember too there were a lot of misplaced concerns early on when the orange dye (and only the dye itself) quickly degraded to a pink color making people think the coolant was failing.

Out of curiosity, and more to the OP's question, would you still recommend Dex-Cool in these engines if they've been running Dex-Cool to this point?

 

With the plethora of "extended-life" coolants available, use whatever toots your horn. There really isn't much difference anymore so long as you use something that says that it is compatible with Dexcool.

 

Thanks guys for the advice. Turns out the guy that I bought it from a couple years ago already changed over to the green stuff so I ended up just completely flushing the system and used a universal antifreeze. Thanks again for the replies. This forum is awesome.