Hey all, I just did a water pump change on a '73 and put the Prestone GM Dexcool (orange) stuff in. I have been reading some reports online that say the stuff may turn to sludge in some cases and I am getting kinda worried. Any thoughts?

Evac the Dexcool right now. That stuff WILL sludge up, and it may be too late already.

You'll probably have to take it to a shop to get the system flushed. I don't think that you can get all of that stuff out on your own.

My friend works for Chevy and sees people add green stuff to the Dexcool all the time, and says it normally takes two or three cycles of the radiator flush machine to clear out the cooling system.

I have run it for over 4 years in my Camaro without one issue.

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70 SS 454 CI Dynoed 684 HP, 702 TQ All Aluminium Fuel Injected Small Block , plus 200 - 500 HP NX nitrous system.

I'm running the stuff in my '98 Blazer. It's the original coolant & has been in use over 50K w/no problems.

I have sludge in the radiator of my 97 s-10 blazer, it was the dexcool. Since I bought this used, I have no idea if it was topped of with something else, or mixed or what, but many have had trouble with it, many have not. I personally would not use it, why take a chance, besides it's not like they stoped making the green stuff.

<font face="Arial,Verdana" size="2">Originally posted by Ryan 79:
Evac the Dexcool right now. That stuff WILL sludge up, </font>

I second that.

I tried it in my 1989 350 GTA (which I no longer own) back last summer. Flushed out all the green stuff and in went Prestone Long Life (very similar stuff to Dexcool). Later that day after a drive I shut it off in a parking lot, and within two minutes the heater diverter valve cracked and blew coolant all over the place. Towed it home, and looked at it the next morning. A second tube on the diverter valve cracked clean off overnight. That was enough for me. Bought a new one from the dealer, flushed out the orange coolant - which also had weird globs of sludge - and refilled with the regular green Prestone. Never had a problem after that. I'm not sure why the diverter valve broke in pieces except to think maybe the plastic was somehow not compatible with the coolant base of the Long Life.

GM had some bulletins concerning Dexcool when it first came out stating it could possibly sludge-up in some vehicles. They didn't recommend its use in older vehicles.

There are some guys that get away with using it, but on the various message boards and mailing lists I used to be on years ago when I owned other vehicles, the consensus seemed to be far more people had problems with it than success.



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'Silver Bullet' 1977 Z-28 413" SB
11.73 @ 115.10 on drag radials
Old Vortec combo:
12.15 @ 110.52

Even though they won't admit it. Dex-Cool IS NOT backward compatible. If you noticed ALL of the vehicles that it was put in from the factory DO NOT have any soldered components. Dex-Cool will literally eat the soldered welds on older (mostly copper) cooling components. Dex-Cool is a OAT (organic acid technology) which could tell you that a chemistry lesson is about to take place. The new HOAT (hybrid organic acid technology) such as G-05 that the new Fords and Chryslers come with is "so far" compatible with any system with a complete flush and fill of the cooling system.

There is a class-action law suit against GM right now concerning Dex-Cool equipped vehicles. The problem with the sludge HAS NOTHING to do with mixing orange and green coolant. All this will do is shorten the orange anti-freeze life from 100K/5 years to 30k/2 years (same as the green).

GM has done research and found the sludge was formed by air pockets in the system causing a "churn" and creating sludge. GM traced this down to faulty radiator caps. Think about what milk does in a blender.


I service about 40 vehicles per day on the average. I have seen Dex-Cool in vehicles with 80k miles on them that the coolant still looked NEW. Then I've seen them with 24k miles on them and it looked like a baby took a big shit inside the radiator. A lot of people have and will use Dex-Cool without incident. But MORE people have problems with it than people who don't.

[This message has been edited by GoldenOne7710 (edited January 16, 2005).]

I just flushed my wife's 97 blazer for the 3 time in 2 yrs, still had that brown sludge coming out. It has to do with the dexcool getting air that makes it sludge up or something like that. I had to take the overfill tankout and literally had brown mud coming out of the bottom. That stuff can get nasty...I say get it flushed out ASAP!!!!!

Oh, an I asked the guy at Advance Auto why the prices of antifreeze have gone up so much. He said they are making a new cross compatible antifreeze and the supply of the old stuff is low so prices have skyrocketed. Don't know about that, but I hate paying $7-10 a gallon for this crap!

One reason it is going up in price is that the ethylene in ethylene glycol is made from a heavier component of natural gas or from crude oil which has been cracked. Both of these feedstock materials have gone up substantially in the last year.

<font face="Arial,Verdana" size="2">Originally posted by BLAZER87:
I just flushed my wife's 97 blazer for the 3 time in 2 yrs, still had that brown sludge coming out. It has to do with the dexcool getting air that makes it sludge up or something like that. I had to take the overfill tankout and literally had brown mud coming out of the bottom. That stuff can get nasty...I say get it flushed out ASAP!!!!!

</font>

Exaxtly what I had to do in my 97, I've flushed mine twice already, I don't know if I'll ever get it all out.

My 1974 has an upgraded aluminum radiator, but some of the other problems metioned w/ Dex-Cool concerns me. Are there any other extended-life anti-freezes that would be OK?

I have a 98 S-10 with the Dexcool, flushed it twice and swapped the water pump before the heat started working again. The Dealer wanted $375 to pressure flush it. F that. Dexcool is trash. Don't use it if you don't have to. 50K miles is about the time it turns to crap. Every GM car I had/have did the same thing at around 50K miles with Dexcool, it sludged up and need significant work to fix it.

I say get rid of the Dexcool and run the green with a 50/50 mix. The green stuff has never let me down. I have seen systems with Dexcool do the nasty sludge. I have YET to see one with Ethelene Glycol (green coolant) do this.

Are you familiar w/ Peaks Global Lifetime Antifreeze & Coolant w/ its lifetime warranty, which also covers your radiator, water pump, heater core & thermostat?

The owner of the shop I work at calls Dex-cool "job insurance" and for good reason. If GM keeps putting Dex-cool in their cars then I won't ever have to worry about having a job. As soon as this "long-life" coolant gets around 50,000 on it turns into a gooey acid that eats apart cooling systems.

It wasted the water pump on my '97 GTP at around 70k.

the 3.1 nd 3.8 engines dont like dex cool for more than 50k either. our shop does about a intake a day on those engines due to gasket failure. the dex get too acidic and eats the gasket alive. then again i have the origional dex in my 98 s10 with 130k on it and its still ok.

every part has its own uniqe effects for every uniqe engine / driver combo.....

<font face="Arial,Verdana" size="2">Originally posted by GoldenOne7710:
...it looked like a baby took a big shit inside the radiator...</font>

Oh maaannn, did you have to get so descriptive? You are bringing back all them memories of those ole forgotten baby diaper changing days. Thank goodness, they grow out of diapers fairly quickly.

No problems with Dex-cool here(yet).&lt;fingers crossed&gt;



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John Wright