Controversial: Where is the evidence that DexCool has no part in HG woes?
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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; So as we all hate to know and admit, the N* has a HG issue. I had to trade my ...
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    Controversial: Where is the evidence that DexCool has no part in HG woes?

    So as we all hate to know and admit, the N* has a HG issue. I had to trade my 98 in due to it.

    I've never heard a valid argument as proof of Dex-Cool causing HG issues, but what about the other way around?

    What intrigues me is the huge percentage of HG woes in 97-99 engines. 60% of the 600 or so that have voted in the HG poll have been 97-99. Are these not the years when Dex-cool was factory fill? I know our approach is innocent until proven guilty, but what about the other question.... where is the evidence that it doesn't play a part?
    http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/122898-northstar-headgasket-cracked-block-bolt-failure-7.html

    The reason for this post is i am having some rough idle at startup from a cold start... very scary, lol. When I bought the car I did a coolant exhaust gas block test, and the liquid didn't change color... but then a few weeks later I wanted to test the antifreeze, and found the reservoir was almost empty!

    So I am about to drain and refill the cooling system, and I am going to go with an extended life coolant, but NOT DexCool. I'll use the tablets/pellets in case it's seepage somewhere else. For those curious, the coolant I'm using is prestone but "safe for all types orange or green" because it has no salicylates. Is there a sound argument against doing so?

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

    The issue is not the coolant it's the pairing between the head and the block. Being that the whole works is aluminum it likes to expand and contract with varying temperature and GM decided it would be smart to use not so coarse threads in their head bolts in the Northstar. Over time the head/block begin to separate because the head bolts loosen and strip out. The gasket itself never fails, the coolant doesn't cause anything, it's the design of the thing that causes the HG failures. They coarsened the thread in the later Northstar builds and it's coming up on 10 years since production for the last run of Sevilles so only time will tell...

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

    Quote Originally Posted by curtc View Post
    The issue is not the coolant it's the pairing between the head and the block. Being that the whole works is aluminum it likes to expand and contract with varying temperature and GM decided it would be smart to use not so coarse threads in their head bolts in the Northstar. Over time the head/block begin to separate because the head bolts loosen and strip out. The gasket itself never fails, the coolant doesn't cause anything, it's the design of the thing that causes the HG failures. They coarsened the thread in the later Northstar builds and it's coming up on 10 years since production for the last run of Sevilles so only time will tell...
    It's a good argument however does not explain the 93-96 lower incidence of HG woes.


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

    The lower numbers of the early years are probably the result of fewer cars left on the road, or fewer people that are driving them visiting this site. They are afterall over 15 years old 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 Mark C View Post
    The lower numbers of the early years are probably the result of fewer cars left on the road, or fewer people that are driving them visiting this site. They are afterall over 15 years old at this time.
    It's plausible, however there's a big jump, and it coincides with a different coolant. I'm not saying that the coolant alone is the problem of course, curtc's reply is the consensus. It's a combination of factors. Open deck heads (where coolant passages are long vs just the waterjacket) and gasket material also have been implicated as potential culprits. However I don't know that such a sharp jump can be explained off by "earlier years, not on the road" etc. If you look at eBay motors, you'll see some of those older models have lots and lots of miles on them.

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

    could also be because 93 to 95 wasn;t it still an option on weather you got a Seville or Deville with the 4.9 and 4.6 ?
    i think my brother had a 95 deville with the 4.9 or maybe it was a 94
    also the seville was northstar only in the sts up untill 94 right ? so 93 and 94 in the sls was still 4.9 ?
    and then the eldorado had the 4.6 standard starting in 93 or was it 94 i forget
    but this may also be the cause to fewer in those years

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

    Quote Originally Posted by mtflight View Post
    So as we all hate to know and admit, the N* has a HG issue.
    Compared to what other engines?
    I've never heard a valid argument as proof of Dex-Cool causing HG issues....
    Because there is no scientific connection.
    What intrigues me is the huge percentage of HG woes in 97-99 engines. 60% of the 600 or so that have voted in the HG poll have been 97-99.
    Why would an owner of one those year models who had NOT experienced a head gasket failure even come to this forum? The poll results are statistically frivolous. Meaningless.
    Since 1996, Dexcool has been the GM factory fill coolant. My 2011 model GM vehicle cooling system was factory filled with Dexcool. You can do the math.
    .... where is the evidence that it doesn't play a part?
    That's not the way the system works. Proving a negative is not required based on more than 200 years of civil law and court precedent.
    So I am about to drain and refill the cooling system, and I am going to go with an extended life coolant, but NOT DexCool.
    Your engine = your choise.
    ....Is there a sound argument against doing so?
    It's not debateable, never mind argumentable. Your mind is made up

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

    one of the main themes in the HG issue for the Northstar, is corrosion of the head gasket metals. With DexCool came extended drain intervals.

    The poll results are epidemiological data. They are not conclusive but they may point to correlations, just like in real world (read about Minesota epidemiologist Ancel Keys and the whole high fat -> heart disease hypothesis that we are still victims of today). Double blind studies are the gold standard and we obviously can't do those here. There is clear correlation indicated in that poll, unless we deliberately excluded years or members. Is it perfect no, is it statistically significant, yes.

    My 1998, 1999, 2003 all had DexCool from the factory, what math am I to do, JimD?

    Some holes in your points too btw. I came to the forum without HG issues, did you have HG issues and is that why you came on the forum?

    And what scientific connections could you possibly make on here? none whatsoever about anything, so why even bother to bring up the "no scientific connection." this is not a scientific board, nor is it a science question. It's an open forum to discuss and to learn from others. There isn't consensus on this and I want to know more which is why I posted.There is nothing wrong with thinking is there? Please don't get offended as that is not my intention.

    Is it fair to say you don't think the Northstar has a headgasket issue? (from your first point) Would any comparison to any other engine satisfy your question?

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

    As mentioned, Dexcool has been in service since 1996 - which still has a relatively low frequency in this poll.

    Also, Dexcool was used in all GM engines 1996 and later, not just the N*. If Dexcool was the cause for gasket failure, the headgasket phenomenon would have extended across all GM engines rather than being isolated to just the N*.

    There is NO hard evidence linking Dexcool to gasket failure. Lots of speculation on the internet, but no proof.

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

    Coolant wars are more fun than oil wars, brake wars, or tire wars.

    Anyone remember the pictures that AJxtcman posted 4 or 5 years ago - the ones of various head bolt holes in Northstar cylinder blocks from various years showing casting porosities, actual cavities in the bolt hole threads, and coolant seepage through the porosities into those bolt holes ?

    My bet is on poor casting technology and quality control, not the coolant per se. NO BOLT, fine or coarse thread, is going to hold worth squat when it's screwed into a wet sandbox.

    Look at 1997-98-99 non-scientific failure rate increases. Right after the mid-1996 engine diagnostics changes to OBD-II and mechanical changes as well. Different manufacturing techniques for the new series of blocks ???

    I'm not quoting or trying to put words into his mouth, but I believe that JimD has opined that steel and aluminum surrounded by an electrolyte will happily corrode away. So, mix the (porous ?) aluminum block holes, the well-grounded steel head bolts and old, slightly acidic coolant: Perfect galvanic (sacrificial) battery - the same process that eats up the inside of your favorite flashlight when the old Eveready batteries go bad.

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

    Quote Originally Posted by drewsdeville View Post
    As mentioned, Dexcool has been in service since 1996 - which still has a relatively low frequency in this poll.

    Also, Dexcool was used in all GM engines 1996 and later, not just the N*. If Dexcool was the cause for gasket failure, the headgasket phenomenon would have extended across all GM engines rather than being isolated to just the N*.

    There is NO hard evidence linking Dexcool to gasket failure. Lots of speculation on the internet, but no proof.
    Good point as to the 1996, however was it during the 1996 year or all 1996 have factory fill Dexcool? It may have been phased in at some time in 1996. Some 1996 cars are manufactured the previous year.

    Regarding other headgaskets the "open deck" design may be a critical aspect. On most engines there are only a few limited contact areas where coolant is directly wetting the head gasket. On the N* it's a very large area, much larger than other engines I've seen. There's a post on the tech forum explaining this but in a nutshell, the headgasket is more critical in open deck.

    http://legacycentral.org/library/literature/deck.htm

    Interestingly enough, apparently Subaru's with die-cast open deck blocks have HG issues too.

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

    That's interesting sub. I agree with you on the threads into the sandbox analogy. I do wonder if there were manufacturing changes from 95-96. I suspect such heavy reliance on a headgasket over such a large area exposed to coolant is a weak spot. Perhaps there weren't enough anti-corrosion additives as was initially though, for the extended drain intervals.

    It's interesting to note that the later Northstars (RWD) do not have an open deck block anymore, and the headgasket material is different.

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

    Quote Originally Posted by submariner409 View Post
    I'm not quoting or trying to put words into his mouth, but I believe that JimD has opined that steel and aluminum surrounded by an electrolyte will happily corrode away. So, mix the (porous ?) aluminum block holes, the well-grounded steel head bolts and old, slightly acidic coolant: Perfect galvanic (sacrificial) battery - the same process that eats up the inside of your favorite flashlight when the old Eveready batteries go bad.
    Well that's quite possible. But it takes a HG breach to get the ménage à trois going.

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

    One point is that ANY coolant goes bad over time. Like it or not, lots of nasties build up in the system and water jackets, so a drain and fill every 3 years is mandatory. The stuff - green or yellow - does have a high load anti-corrosion package, but heat and trace gas weeps (in ANY engine) slowly destroys the coolant's capability for corrosion control. Bottom line: change it religiously.

    Want anal ??? Every 3 or 4 months, while I'm checking either the car or truck fluids and other stuff, I siphon off 2 quarts of coolant from the reservoir - cold. Refill with fresh mix - I keep 2 gallons ready. At the end of a year I have exchanged 2 gallons of coolant in each vehicle, and what siphons out is crystal clear yellow.

    You should see some of the coolant specs for large marine diesels.

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

    Quote Originally Posted by mtflight View Post
    Well that's quite possible. But it takes a HG breach to get the ménage à trois going.
    Not so - the corroding coolant seeps into the head bolt holes through the porous block or cavities from the pressurized cooling passages. The head gasket can be solid as a rock UNTIL the bolts start to pull........then you get coolant in a (the) cylinder(s).

    EDIT: And here's an engine builder's take: Northstar uses thread sealant on the head bolt holes - why ?? It's certainly not to prevent the bolts from loosening...........I have built over 43 Olds 455's for every sort of duty and have NEVER used a sealer on head bolt threads whether stock, ARP, or studs. Matter of fact, most engine building people and books will tell you NOT to use stuff on the bolt threads because it might mess up proper torque settings.

    I think GM uses thread sealer as a stopgap "gasket" sealant insurance.

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