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Northstar Engines and System Technical Discussion Discussion, Thoughts on Dex-Cool and Head Gaskets in Cadillac Engine Technical Discussion; Originally Posted by osu411yamaha ....Average lifespan of northstar engine=length of GM warranty.... My English suffers at this time of the ...
  1. #31
    JimD is offline Cadillac Owners Connoisseur
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    Re: Thoughts on Dex-Cool and Head Gaskets

    Quote Originally Posted by osu411yamaha View Post
    ....Average lifespan of northstar engine=length of GM warranty....
    My English suffers at this time of the day so cut me a little slack.

    But your position is unsupportable. In otherwords, bullshit.

  2. #32
    ewill3rd is offline Cadillac Technician
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    Re: Thoughts on Dex-Cool and Head Gaskets

    Jim,
    While I find your theoretical model entertaining it has little basis in reality.

    The head gaskets fail BECAUSE the bolts pull. There is nothing wrong with the gaskets, the problem is that the bolts pull and clamping pressure is lost.
    I think you are talking about "electrolysis" not "oxidation". While the two have similar end results, if you want to split hairs... and it seems many people here do... well I just thought I'd mention it.
    Most (if not all) GM engines these days are cast aluminum and have ferrous bolts. The bolts are typically threaded into the water jacket so the bolts are in constant contact with the coolant.
    Why then don't all GM engines have head gasket problems?
    As stated time and time again this is a problem that was addressed in production by changing thread pitch and bolting. The rest of the design is still the same.

    I hate to keep getting drawn into this garbage but I can't just leave all this X-files automotive my crap out there for people to believe.

    Its cool if you don't want to believe what I say, but the truth is out there.

  3. #33
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    Re: Thoughts on Dex-Cool and Head Gaskets

    Folks -

    I think Jim may be onto something, without "splitting hairs", it seems very strange and a very unlikely explanation that the head bolts would hold for years and even perhaps 100k miles and then all of a sudden just "let go". I also have a very hard time believing that so many blocks suddenly had a manufacturing/production issue starting in 2007 that caused them to suddenly be manufactured with porosity issues or lower tensile strength.

    Also, I think we are now finally beginning to see head gaskets going on 2000+ MY vehicles, so I'm not sure the change in head bolt pitch is necessarily the long term solution.

    My fundamental point is only that if it is true that DEXCOOL turns acidic (pH below 7) when exposed to air for a long period of time, as would occur with a small/slow leak past the HGs, that it may very well be the underlying cause of the head bolt hole thread damage. IF that is true, then it makes a strong case to switch from DEXCOOL to a different coolant which is less likely to cause that problem (less likely to become acidic when exposed to air).

    Some have argued that the DEXCOOL in our Northstar engines is always exposed to air on a regular basis. I'm not fully convinced of the validity of this comment. Although it is true that there is a small quantity of air contained in the expansion space in the small secondary tank, the entire system is designed to be sealed and closed. If it is true that air reacts with some of the buffers in the DEXCOOL, it may well be the case that there is a sufficient concentration of buffers to handle the reaction with the air in the reserve tank and keep the coolant basic. The behavior of the coolant may be very different when exposed to air for a long period of time with an unlimited quantity of air to react with. I have not tested this point to validate it, I am simply sharing "claims" I have read about in my research, however it would be easy enough for any of us to test this. I do know for sure that GM has recommended that people who own vehicles with engines covered by the lawsuit were told to replace their radiator caps and to make sure that the coolant system was completely air tight. Also, cars equipped with DEXCOOL from the factory all have sealed, air tight, secondary reserve tanks as compared to the old style which was open to the air. I think this further supports the idea that DEXCOOL has issues when exposed to the atmosphere for an extended period of time AND that GM was aware of that fact from day 1.

    One other important point I'd like to share. As I was doing my research on DEXCOOL, I learned that it takes quite a few thousands of miles of the coolant being in the engine until the additives become effective. Now, I don't claim to know how many miles or the details of how this works, however if this is an accurate point, then it seems to me that frequent changes of DEXCOOL may be more detrimental than beneficial. It is my understanding that one reason the G05 coolants have "some" silicates added is to provide immediate protection until the OAT components become active. This may provide a partial explanation for why some of the head gaskets appear "rusty" or "worn" when removed. The vehicle may in effect be operating for some period of time without any real protection . . .

    Also, if DEXCOOL is so wonderful, how come every other auto manufacturer on the planet has flat out rejected that coolant? Ford actually tested it in one vehicle for a few years and concluded they would not deploy DEXCOOL in another vehicle ever again (due to gasket issues). To the best of my knowledge, they are now (and have been for quite some time) using a G05 spec Motorcraft coolant.

    Simply put, there ARE some issues with DEXCOOL and I'm unsure whether frequent changes of this coolant are sufficient to truly address the known issues.

    The discussion and range of opinions being expressed in this thread, and also in this forum, most broadly proves to me that nobody definitively knows the underlying failure mode and sequence for these head gasket failures. Given the apparent uncertainty and the possibility that DEXCOOL MAY be playing some part in the overall failure of the head gasket (either through damage to the gasket itself or to the head bolt hole threads or both) the question I'm asking is simply this: "Why not switch to a different coolant with a proven track record and potentially less risks associated with it than the DEXCOOL?"

    I've listed at least two specific coolants, both of which are "long life" and from my research it seems that neither of them suffer from either the concerns typically associated with DEXCOOL or any other new issues not associated with DEXCOOL.

    Andrew

  4. #34
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    Re: Thoughts on Dex-Cool and Head Gaskets

    Andrew, all that sounds logical and could be true, but you have to ask yourself, why not ALL GM engines then? As I said earlier, my wife's '96 Bonneville has 160K on it and never had a gasket problem AND it does not have a sealed reservoir. It expels ambient air with every heat cycle and draws in fresh air with every cool down. The coolant in the tank is also drawn into the radiator with every cool down and expelled into the tank with every heat cycle. Under your theory, that stuff should be even more acidic than what is in the Northstars. You also have to ask yourself why the thermostat gaskets never leak or the water pump gaskets? There is NO problem switching coolants if you are leary of Dex and I would do so in a New York minute if I thought there was a problem. I just don't see the problem. Why only Northstars and why only head gaskets?

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    Re: Thoughts on Dex-Cool and Head Gaskets

    Hi Ranger -

    I am the first to admit I don't have all the answers.

    Was DEXCOOL the original fill on your Bonneville? Are you also the original owner? I only ask because if not, then perhaps the gasket was upgraded before you got the car . . .

    By the way, I know that car well and like it very much. I have owned two 1995 Buick LeSabres which are basically the same drive train and chassis with softer suspension tuning. They both had the open reservoir and were filled with traditional green silicated coolant when I got them.

    I do know that the 3.8 engine is a cast iron block and head so a very different metallurgy than the Northstar. Your point about water jacket gaskets and such may simply be that the materials they are composed of are not reactive with DEXCOOL. I know that those kinds of gaskets are sometimes paper, rubberized paper, cork, etc. I don't know what they are on the Northstar or the 3.8L off hand. I do know that DEXCOOL is said to have issues with nylon gaskets, primarily when the DEXCOOL turns acidic, and when they are not properly protected from contact with DEXCOOL (like the lower intake manifold gasket on the 3.8). Apparently the redesigned lower intake manifold gaskets for that engine are either made of nylon and protected by teflon or are made of completely different materials now.

    My guess is that you have always maintained this car well and probably changed the coolant regularly and before it became acidic. This as it seems to me that any lack of maintenance of the DEXCOOL risks causing issues . . .

    Andrew

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    Re: Thoughts on Dex-Cool and Head Gaskets

    Factory fill was Dex. I bought the car with 25K on it.

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    Re: Thoughts on Dex-Cool and Head Gaskets


    This thread is just awesome.

    BTW... NO cooling system is "sealed".

    The "pressure" cap maintains approximately 15 psi during hot operation.
    MOST cars have a reservoir that is OPEN TO THE ATMOSPHERE.
    The REST of them have a negative pressure relief that allows AIR to re-enter the system when the pressure falls off.
    The system CANNOT be "sealed" or things will begin to explode under operation.
    Some portion of the Dex Cool is always exposed to the atmosphere.

    Yeah, magically the same engines, made by the same company at the same plant with the same specifications could be subject to the same failure. Pretty remarkable I know, but it is possible. Amazing to me also is how this issue severely declined after GM looked at it and made changes to the block in production, including thread pitch. That's probably just a coincidence though.
    LS engines have been in production with an aluminum block since '97. I can count on zero fingers how many head gaskets I have seen fail yet they use the same coolant.

    While I find this episode of mythbusters entertaining, I think I'll pass on visiting here again.
    It is obvious that several have convinced themselves that the sky is indeed falling.

    Actually you know what it is that is causing the headgaskets to go? Global warming.
    Yep, that's it.

    Okay so you think Dex Cool is to blame and you want to use a different coolant. Go ahead, nobody is stopping you. In fact it might be the greatest idea since television.

    I'm sorry.. I didn't mean to interrupt all this meaningless speculation with actual facts.

    Please continue....

    I'm out.

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    Re: Thoughts on Dex-Cool and Head Gaskets

    I have to disagree with many of these posts based on my personal experiences. I will post some pics of head gaskets and i can guarantee that it's more of a head gasket issue than a bolt pulling issue. I am almost sure the head gasket fails first, leaking a little antifreeze in the bolt holes (meanwhile car still runs fine and not overheating because the clamping pressure is not allowing any combustion gasses into the cooling system) but when the catalyst (antifreeze) sits in the bolts holes the galvanic reaction takes places and eats away the threads in the block, and we all know what happens next . Almost all of the head gaskets I've pulled off have been destroyed by lack of cooling system maintenance. Let's not forget that these are open deck blocks where the 3.8's and SBC's are all closed deck. You don't have the amount of gasket/antifreeze surface area contact as you do with open deck blocks. I will post some head gasket pics later.

  9. #39
    jeffrsmith is offline Cadillac Owners Fanatic
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    Re: Thoughts on Dex-Cool and Head Gaskets

    Let me help. These are pics of my HGs that let go at 92K. Thought I would throw in a couple of pics of the Head Bolts as well.




    [IMG][/IMG]

    [IMG][/IMG][IMG][/IMG]

    [IMG][/IMG][IMG][/IMG]

    [IMG][/IMG][IMG][/IMG]

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    Re: Thoughts on Dex-Cool and Head Gaskets

    Boy, those gaskets sure look rusty and deteriorated - why?

  11. #41
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    Re: Thoughts on Dex-Cool and Head Gaskets

    .........actually, not bad for 95K head gaskets. Considering the condition of some stuff we pull out of Olds 455's and GM 454's at 100K.

    Head bolts, head studs, fabric gaskets, copper gaskets, stainless gaskets, copper O-rings. All go sooner or later. Try to get the remains of a broken head bolt out of an Olds 455 iron block - WooHoo !

    What you don't see is the open deck Northstar design which is hidden by the gaskets, but you can imagine the narrow cylinder seal area by looking at the gasket depression around the steam holes.

    So.............which came first: The chicken or the egg ???


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    Re: Thoughts on Dex-Cool and Head Gaskets


  13. #43
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    Re: Thoughts on Dex-Cool and Head Gaskets

    That's about what they all look like. If the block was the problem, the gaskets should look OK. It's obvious those gaskets couldn't seal anymore. Most naturally aspirated engines are open deck, but I bet the supercharged 4.4L Northstar won't experience this issue.

  14. #44
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    Re: Thoughts on Dex-Cool and Head Gaskets

    Quote Originally Posted by ewill3rd View Post
    What’s a head gasket?

  15. #45
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    Re: Thoughts on Dex-Cool and Head Gaskets

    Someone please Google "open deck cylinder block" and compare the Northstar block construction to, say a GM 454, Chevy 327, 350, Olds 455 - many other cast iron "closed deck" blocks.

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