Hello folks!!

The daughter has just acquired a new-to-her 7th gen N-body (94' Skylark) with 3100 V6. I've did some homework and read lots of coolant related issues this engine has a reputation for. Planning on doing a coolant replacement on this buggy when the weather caves in to springtime soon! I pondered which way to go with the coolant itself and the light came on -all the wonderful experience and opinions out here in J-Body Land!! :-)
My personal thoughts are, that aluminum has been used in engine components going way way back - from intake manifolds to heads and now even blocks. Haven't read much of any improvement in engine gaskets lasting any longer since the DexCool came along. Seems as if manifold and head gaskets are as trouble prone now as ever , so drain , rinse and replacement with the green stuff will work just fine.

Since our J-Bodies have been Aluminum headed since 1987, and the 2-8 /3.1 are more reliable cousins , I'm betting my boots that everyone out here has something to add, and I'd Love to listen!! I'm hoping to learn a thing or 2 in the process!!

Also this car has a closed cooling system, the recovery tank is dirty, but the coolant inside is a pretty green color .

Thanks to everyone in advance for the input!!



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Lower intakes are the faults. That is the only issue with 3x00. Just replace them with metal ones. Wot-tech.co sells them and also check 60degreev6.com for other question. I own 4 3x00 engines and they are build and abused lol.




On the inside my car looks like a fighter jet.

everything i've heard or read about dexcool was bad. it is supposed to last 100,00 miles but seems to turn into gunk if you wait that long to flush it. do a good flush and go with the green stuff, no more than a 50/50 mix. any more thaqn 50% antifreeze will diminish it's effectiveness. i also went to napa to buy an antifreeze tester. the guy there told me you cannot use it on both types of coolant. meaning you can't test the green stuff and then test some dexcool with the same tester. he said it wouldnt give a correct reading after that and you need to have a tester for each kind of coolant. i never heard of that before and i don't know if they wre just trying to sell me another tester. thats just what he told me. as for blown head and intake gaskets it is a very common problem in most cars now. the gasket material is not as good and the plastic intakes just cannot take the heat. i have two late 90s buick lesabres with the 3800 and have had to replace the plastic intakes and gaskets on both. the intake just crumble from the heat and allow coolant into the cylinders causing hydrolock. if you catch it early it is not to bad. you will usually get a check engine light with a cylinder missfire code. this is from small amounts of coolant leaking into the cylinder and not allowing it to fire. if your check engine light starts blinking the gasket or intake has totally failed and you are seconds away from hydrolock. i know this firsthand and it means alot of work.

I had a 3.1 in my 1997 Grand Am, same as the Skylark. I had to have the head gasket replaced and later on the lower intake manifold gasket needed replacing.

What I was able to find out, and there was a class action lawsuit regarding it as well, is that whatever gasket material GM was using at the time would be broken down on a molecular level by the DexCool.

My opinion--do a pressure test to make sure there aren't leaks you don't know about, then just drain what's in there and put the yellow universal stuff in the place of the DexCool and you should be good to go.

I've always bought 100% green antifreeze and dilute to a 50% split. Never had a head gasket issue with any car/truck that I have owned since I started driving in 1979.

The ready to use stuff is a joke!

I purchased a 2005 Chevy Equinox in May of 2004 with the 3.4 L V-6 engine in it.. I have religiously maintained this vehicle including four BG flushes and treatments for the tranny and cooling system. Oil/filter changed every 3K miles. At 65K, I noticed the vehicle started using coolant and after about a month and a half determined the head gaskets were blowing. I knew of Dexcrap's problems early on and only left it in my vehicle until the 3 year/ 36K mile warranty had elapsed, but unfortunately, the damage had been done by then.
I pulled the heads and sure enough, the head gaskets had blown from a small water hole about 1/2" from the cylinder bore to the cylinder bore. Funny thing about it was that the small water holes were partially blocked with the jelly like residue that Dexcrap leaves behind everywhere in your cooling system. The intake gasket had no issues (other than the Dexcrap gel being throughout the water passages) because GM began to use a different material on the gaskets by 2005. During the head replacement ordeal, I must have gotten two to three pounds of red Dexcool gel out of the block, heads and radiator even though I hadn't used it for 30K miles ! Keep in mind, in the 65K miles we had driven this vehicle, the "100K mile" coolant had been changed twice within the first year because of gelling, smell, and permanent staining to the overflow canister, twice more with BG flushes before I replaced it twice with flushes with the green stuff.
My vehicle now has 90K miles and I still get the red jello-like crap in my overflow canister even AFTER back flushing the system and using the green stuff for 55K miles! needless to say, I don't recommend using Dexcrap under any circumstances.
I am lead to believe that Dexcool works well in some GM apps, but it doesn't work well in 60 degree V-6 applications for sure,
Another thing to remember - NEVER run Dexcool low or it will acidify and start attacking aluminum components in your cooling system. Other than the fact that Dexcool doesn't attack engine bearings when it gets into your oil, there are no benefits in using it.
What to replace it with ? Prestone has a very good multi-use green coolant that works VERY well. I have used it in my wife's Equinox for 55K miles with no complaints whatsoever.
I have worked in the engine machine shop business for over 20 years, (a lot of it doing warranty work for several GM dealers), and believe me, while they are having less issues with newer GM vehicles with Dexcool,, the older ones do not like it.




~ Mike ~

Well this certainly turns out to be a unanimous decision!!

Plenty of good information & advice! This Buick has 132K on the clock , and very well might have had corrected issues in it's earlier travels. The engine is quiet, smooth and powerful. I also tried to do a little reading online and it seems that DexCool didn't come factory installed till 1996, and since this one is an "94 chances are it never saw that ole stuff to begin with. I know it doesn't have a sticker about under the hood and it probably would that early in the usage. I'll definitely keep a constant look under the hood watching for signs of woe.

It's good to know the old stuff is still the best stuff! New is not always the better.

Thanks for all the input folks!! I sure have learned a lot!!



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Never used it in my mazda or wifes honda or sunny.All the info on issues with it is here already.I would use some lime away to flush the system out myself.I have used this and just drained and refilled with my well water and 1 bottle lime away(or dollar generals off brand name or others same stuff) and run vehicle to temp.Then let cool some drain,refill with water and run car for 15-20 minutes heat on high and using cardboard speeds the process on 1st warm up.This stuff will remove anything inside the block,heater core and radiator and is safe to use.I did 2 clean water flushes after the lime away to make sure the fluid coming out was CLEAN and no more goo or crap built up inside my block and so forth.I used this on my mazda trk and did have a new rad and heater core just cleaning the mess out from 20plus yrs of wear and (made the mistake of using bars leak) yrs ago to fix my leaky wp on the truck.I did replace my wp at the time of a new rad,and core so everything was new just flushing my block mostly to clear the passages out.I think that covers it.As for my mother in laws old 98 malibu yeah the intake gasket bit the dust leaking coolant(aka dexcool) and had gasket done,but we soon sold the car after the fact and she got a 08 civic.As for the old car it still runs fine (buddy bought it)for his son and ok to my knowledge to this day.

The green ethylene glycol is definitely better. It's worse for the environment which was one of dex cools sales pitches. As a result it doesn't have the lubricants and corrosion resistant properties that the green stuff has. Definitely go with the green stuff if you're doing a good flush. I've done that in 2 vehicles so far.


"In Oldskool we trust"

I have to pipe in here as well.

Had the 3100 in my wife's 97 Grand Am. Had the intake leak. Dexcool turned to pudding in the engine. it was not pretty.

If you are keeping it, go green and stay green.

I never liked the dexcool. And only my father runs in his s10. No one else I know runs it.




On the inside my car looks like a fighter jet.