What's The Story With DexCool?

Black Sun 5.0

Founding Member
Mar 23, 2002
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L.I., N.Y.
I'm asking only because after only 3 or 4 months since I replaced my radiator, I have what looks like a mad amount of brown rust in my coolant. It initially looked orange, like the shop put dexcool in the system. Doesn't that stuff rust out the cooling systems on cars? I thought it was oil in the coolant at first, but I haven't lost any coolant in 2500 miles and it's clean.
 
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I run dex in my '90 with the factory brass radiator and haven't had any problems. The car runs a little cooler too.

You have to completely flush the green first though ... if someone mixed the two then (from what I've heard) they will sludge up.
 
Dex cool is a GM developed version of coolant that doesn't use the traditional ingreident of Etholyn-Gylcol. They use a different chemical that doesn't break down as fast and has more water like cooling properties.

Early versions of GM dex coolant are known for rusting out your cooling system. I think GM is in a lawsuit over it now.. Later versions have it corrected.
 
That's probably what happened. I don't know why the shop would suddenly switch over to the dexcool, but I seriously have to have my system flushed this week. It's bad, real bad. Fortunately, the car is staying cool in the high heat this week.
 
that stuff is some of the biggest crap made.i'm constantly putting water pumps,intake gaskets and intake manifold fittings in gm vehicles at work because of this crap.i wouldn't put that stuff in a yugo.
 
If you want to see some interesting reading, just Google 'dexcool' -- lots of problems, class action suits, etc.

The bigger problems seem to occur when DexCool is mixed with traditional antifreeze. But once I read about it, I took it out of mine. It had been in for a month or two on a fresh rebuild. I probably used 30-35 gallons of distilled water and flushed until it ran completely clear (be sure heater valve is open if that's applicable to the Stangs). You can't measure 'clear' by looking at the stream flowing out of the radiator drain valve. You have to catch some in a clear container and hold it up. You want to get all that stuff out. Then just run the 'green' stuff with distilled water to minimize any internal mineral deposits from tap water.
 
I work in a shop and do a lot of cooling system repairs. Dexcool is less toxic and more enviromentally friendly. That is probally the main reason you see more and more Dexcool in newer cars. It is also better on alumimum, and as said before, is suposed to be a better "coolant". Other manufactures such as Toyota use Dexcool, except Toyota adds more Red Die. Dexcool is really orange.

Where the manufacturers went wrong is advertising the stuff as "5 year 100K miles" which is complete BS. It turns to straight up mud and cloggs cooling systems, I call it when it gets old "Dexsludge". Another major issues is when people mix the regular Green Glysol in it, turns to mud.

When you switch to one to the other, it is very important to completly flush out the old coolant. Michael Yount goes a little far with the distilled, but to each his own. I would just disconnect the upper hose, aim it the best you can towards a drain, put a garden hose in the radiator, turn on the hose and the car and flush it that way. Pulling the T-stat helps. Then fully drain the system, then do the mix between the new coolant and distilled water.
 
If you've ever lived in a part of the country that has really hard water (Acworth don't qualify) you'd see the wisdom of using distilled instead of tap water. I completely understand that if you're working in a shop trying to make a living working on others' cars, there's a limit to what you can do profitably. But if you're doing it yourself at home - running distilled water is a no-brainer. Tap water has lots of mineral content - and that stuff loves to become undisolved - and relocated on the internal parts of your engine and radiator/heater cores clogging them and causing poor thermal performance.

I wish I had pics of what appears in the bottom of a home water heater after 3 or 4 years of having extremely hard FL or Houston, TX water running through them. Quite literally POUNDS of rocks -- rocks made of minerals that became undissolved from the water and deposited in the bottom of the water heaters leading to very short waterheater lives. Only takes a little bit of that to sell someone on the benefits of distilled water in a cooling system.

Like I said earlier, notwithstanding the purported benefits of DexCool, google it. Literally thousands of hits on lawsuits, consumer complaints, etc. Where there is smoke, there is usually fire. And where there is sludge in the cooling system, there is usually DexCool.
 
I was refering to the "get the old crap out" process, when actuall mixing coolant, distilled all the way, in my car's at least.

Your suposed to drain 1qt or so from your hot water heater every month, (drains from the bottom, that stuff gets nasty)says it in most instruction manuals, but no one reads them, and in this house, the nossel is so hard to get to.
 
I think we're preaching the same story here.

The reason they specify the regular draining is because they know what's in tap water too.

The problem with running tap water through to flush is that it's clear too. So once you go to swap in the distilled, you have to flush out the tap water; and because it's clear, you then have no way of knowing when you've gotten all the tap water out. Better to simply flush with distilled -- you'll know you've gotten all the old stuff (water and antifreeze) out because it'll run clear. No since in running distilled if you've left some tap water in there from the flush job.
 
How 'bout that new Prestone Orange stuff??? I put it in with Water Wetter :mad: If it kills my brand new Fluidyne I will be :fuss: :fuss: :fuss: :damnit: BTW, that regular yellow Prestone sure leaves a lot of silica-like white stuff anytime it evaporates, are you guys sure its not bad for waterpumps?
 
the problem with mixing traditional antifreeze and dexcool are the weights of the fluids, I don't remember which, but one type is heavier and will sit around the bottom, it doesn't mix well. from what I've heard, and I'm not sure if I remember, but on aluminum heads with traditional antifreeze, teh electrical charge that comes out of teh plugs and through the heads changes teh coolant somehow and becomes corrosive to alum. so manufacturers began to develop something that wouldn't be problematic. dex-cool may suck, but you will realise that german manufacturers use a type of extended-life, aluminum safe coolant themselves, it's usually blue. and german manufacturers are usually a few years (if not decades) ahead of us in engineering.
 
I put some in my Probe GT and quickly got it out after researching the internet on it. I had just replaced the radiator and did not want to ruin it. The problem seems to lie in lack of maintenance and mixing coolant. Either way its bad news unless your car came with it from the factory.
 
If you drain and refill every year or every other year you will not have any problems ... of course it isn't a 100K mile coolant. :rolleyes:
My fiances '98 FireChicken has had it's coolant changed every 2 years (by me) and the cooling system has been nothing but great on the car and we've had it since new and it has 80K on it now.

If someone advertised 100K mile oil would you run it for that without changing it ... no, of course not.
 
TheRedBlur said:
the problem with mixing traditional antifreeze and dexcool are the weights of the fluids, I don't remember which, but one type is heavier and will sit around the bottom, it doesn't mix well. from what I've heard, and I'm not sure if I remember, but on aluminum heads with traditional antifreeze, teh electrical charge that comes out of teh plugs and through the heads changes teh coolant somehow and becomes corrosive to alum. so manufacturers began to develop something that wouldn't be problematic. dex-cool may suck, but you will realise that german manufacturers use a type of extended-life, aluminum safe coolant themselves, it's usually blue. and german manufacturers are usually a few years (if not decades) ahead of us in engineering.

Well, actually they will mix, and turn straight to sludge. Good point about the alumimum part, that is an issue.

The point is that dex-cool is good coolant but needs to be "watched".
 
Hope I`m not out to lunch on this,but what about other extended life antifreeze,(name your mfg),that`s not directly marketed as GM "Dexcool",but says "compatible" with Dexcool on the label.
What`s the difference,if any?