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Cadillac Seville / Cadillac Eldorado Forum Discussion, Controversial: Where is the evidence that DexCool has no part in HG woes? in Past Cadillac Vehicle Discussion; As I've posted elsewhere, it turns out that Dex-Cool and other long life coolants have 2-ethylhexanoic acid in either the ...
  1. #31
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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    As I've posted elsewhere, it turns out that Dex-Cool and other long life coolants have 2-ethylhexanoic acid in either the sodium 2-ethylhexanoate or potassium 2-ethylhexanoate, as part of the anti-corrosion package. They are good coolants and they work as indicated. The issue is that 2-ethylhexanoic acid is a plasticizer. This means that it softens and eventually destroys certain polymers such as silicone rubber and Nylon 6,6.

    GM pioneered the long-life coolant scene, and it was a good idea that has been widely adapted (Honda and Toyota warn their patrons to avoid coolant with 2-ethylhexanoate). Unfortunately it seems like some gaskets had these polymers that were degraded or plasticized and then came a huge lawsuit for the intake manifold gasket in many cars. The solution was to change the gasket materials to avoid silicone rubber or nylon 6,6. This came a bit too late. How much silicone rubber is in the original Northstar head gasket? I think there is at least some, and what we call the "unscientific poll" which is an epidemiological poll is a smoking gun as far as owner experience in the forum.

    I believe it goes like this:
    2-ethylhexanoate in coolant softens the gasket and it begins to corrode (may have copper or brass?)
    coolant may seep into bolt holes, causing a reduction of clamping force
    full blown head gasket failure

    A longer coarser, wider bolt hole would slow down the full blown gasket failure, as would a different revised gasket material devoid of silicone rubber and nylon 6,6. GM and other manufacturers do not use these materials anymore in internal engine parts that are in contact with coolant. They learned their lesson. We, Northstar owners were accidental guinea pigs.

    The problem wasn't really the bolt holes (at least not before the 2-ethylhexanoate came along in late 1996). As with most things, hindsight is 20/20.

  2. #32
    drewsdeville is offline Cadillac Owners Master
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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    So under your theory, the root problem is gasket failure, not block thread failure.

    I agree. I find the magnitude of gasket degration on these relatively recent engines (10-15 years) to be astounding. We aren't talking about some blown sections of otherwise decent gasket due to loss of clamping force - pictures show entire gaskets rotted right out - they look 3 times their age - you'd expect to see those pictures when pulling apart a barn find pickup truck, not a modern, ten year old, 100k mile engine.

    The bolt hole problem parallels other engines - I don't see any special N*-only phenomenon when it comes to the block threads. This happens to many modern aluminum engines - even the beloved Hondas. But, their gaskets rarely, if ever, look as nasty as these...

    We all seem to agree that the N* isn't a "regular" HG failure. So whats the difference between this one and other manfacturers? To me, the overall gasket condition is the big red flag. Everything else seems relatively "normal" to me as far as a modern aluminum engine HG failure and replacement.

    On top of that, 2000+ HG threads are gaining quite a bit of popularity, also supporting your theory.

  3. #33
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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    The threads attached to the bolts, aka "pulled head bolts" are probably a result of galvanic corrosion, which requires an inert electrolyte (e.g., potassium or sodium) in the bolt hole to begin with (a head gasket failure).

    If the head gasket has a silicone rubber or nylon 6,6 component it would erode when in prolonged contact with the 2-ethyhexanoate (2-EHA) exacerbated by the open-deck waterjacket design around the cylinders. Very sad.

    GM and others have learned. I think that GM uses different gasket materials now to be forward compatible with Dex-Cool. The supercharged Northstar has MLS gaskets. I know that Cometic makes an aftermarket MLS head gasket for the Northstar, and it has Viton a fluoroelastomer that is structurally much different than silicone rubber (elastomer), thus is touted to be chemical resistant.

    The reason we don't see many rotted out Honda/Accura or Toyota/Lexus head gaskets is that they are very adamant about letting their patrons know to avoid Dex-Cool or other coolants with 2-EHA. The Japanese coolants don't have 2-EHA in their formulation.

  4. #34
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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    This all sounds logical, but then I have to ask, why didn't I have any problems with my wife's '96 3800? It made it to 185K with no HG (or any other cooling system gasket) failure. Likewise my daughters Grand Am 3.4 with about 125K at this time.

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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    Quote Originally Posted by Ranger View Post
    This all sounds logical, but then I have to ask, why didn't I have any problems with my wife's '96 3800? It made it to 185K with no HG (or any other cooling system gasket) failure. Likewise my daughters Grand Am 3.4 with about 125K at this time.
    The answer is probably there is less [or none] silicone rubber in the head gasket or perhaps the gasket was not in as much contact with coolant (closed deck design?)

    Different designs and materials. Much the same way that we didn't suffer the disintegrated intake manifold gasket issue that confirmed the class action lawsuit and settlement a few years ago.

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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    So then we've come full circle. Is Dex the problem or the open deck? Maybe both when used in combination? Either way, I think we'd pretty much all agree that the HGs go first. Just wish I knew for sure if Dex was the problem or if it was reformulated and no longer is.

  7. #37
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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    I'd think the gaskets were reformulated. There's nothing wrong with Dexcool. It works great as long as there aren't any silicone rubber or nylon 6,6 materials in contact. Virtually all coolant manufacturers have joined and have the OAT extended coolants. Of course the only problem with the conventional green coolants was the silicates depleted every 2 years.

  8. #38
    Northstar125 is offline Cadillac Owners Fanatic
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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    I am not saying that dex causes the Northstar headgasket failure. (Seems there was a crappy bolt design).


    But read this: http://www.dex-cool.net/


    This explains about the dex cool and the gaskets. The GM 3.4 seem to have been the worst plagued. 3.1 had it's problems as well.

    The 3800 engines while being bullet proof have been plagued with gasket issues as well.


    Here's the kicker: A LOT of people don't know their gaskets are bad or don't "think" they have a problem. But when you end up with a rod knock and a couple of spun bearings what is to blame?

    These gaskets and the coolant........

  9. #39
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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    Well off the bat nylon66 is nylon 6,6. We now know it will be degraded by 2-EHA. Silicone rubber as well. Seems like someone didn't do their homework in matching these materials. Thanks for posting!

    The troublesome part is some extended coolants use potassium 2-ethylhexaonate while others use sodium 2-ethylhexaonate. That's still 2-EHA. The part about Dex-cool becoming acidic wasn't necessary. 2-EHA is all that's needed to degrade nylon 6,6 or silicone rubber.

    It just dawned on me. We have revised water pump and intake manifold gaskets. I wonder if it's because they were known leakers with dexcool?

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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    Interesting article. I wonder what the date of it was.

  11. #41
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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    If you replace enough 3400/ 3100 intake manifold gaskets, you get a chance to see what dex-cool does to those gaskets.

    Unfortunatley, dex-cool has been reformulated a few times, gasket materials and kits have been updated.

    Dex-cool is a common demoninator in a few GM headache engine problems. It's function was to stretch out service intervals for coolant changes. Unfortunately, it didn't work. Just service your vehicle when it's due and save yourself some extra headaches.

    Not to say, that certain engine designs weren't "flawed" and this only "compounded" the problem but servicing your vechile is a part of ownership.

    Driving it till the wheels fall off, isn't a good thing unless you're into that sort of thing.

  12. #42
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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    I believe that article was created a couple (3-4) years ago. But not sure on the exact date.

    It was written by the gearheads from pontiacbonnevilleclub.com.

    It seems GM has updated the gaskets (now they are aluminum). That has fixed the problems (at least on the 3800 engine). UIM melting was another big problem.

    That's not Northstar related though so I'll leave that alone. haha

  13. #43
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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    3400/3100 intake gaskets have gone the same route. Yet, how many cars have been junked or ruined over this nonsense.

    Upper intake manifold melting was another joke on the 3800's. I see the series III motors are back to aluminum intakes.

    GM has always had some great ideas but execution of the idea, that has always been another story.

  14. #44
    Northstar125 is offline Cadillac Owners Fanatic
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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    Yup. The series 1 3800 from 88-92 had aluminum intake manifolds.

    I dont know why they ever even went to plastic? Probably saved them $1 per car...

  15. #45
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    Re: Controversial: Where is the evidence that DexCool has no part in HG woes?

    Correct.

    Saved a dollar up front, to lose it on the backend in warranty claims. Then they wonder why then almost went under......

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