Thoughts on Dex-Cool and Head Gaskets
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Northstar Engines and System Technical Discussion Discussion, Thoughts on Dex-Cool and Head Gaskets in Cadillac Engine Technical Discussion; I've been doing a whole lot of research on Dex-Cool and trying to determine if I want to leave this ...
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    Thoughts on Dex-Cool and Head Gaskets

    I've been doing a whole lot of research on Dex-Cool and trying to determine if I want to leave this coolant in my Northstar or pull it out and replace with something like Zerex G05 or Peak Global.

    Apparently DexCool can become acidic over time if it is either a) not maintained, or b) exposed to air due to minor leaks in the coolant system. Over time, the acidity of the Dex-Cool can damage all kinds of gaskets. A number of folks who regularly replace head gaskets in Northstars have reported that the condition of the gaskets pulled from cars still running Dex-Cool often appear to be more worn out and rusty than typically seen with cars not running Dex-Cool. One person who has described this pattern is Jake (97EldoCoupe).

    Now, we already know for sure that Dex-Cool can severely damage gaskets that have a Nylon carrier. The best description of this I've seen to date is here:

    http://www.zillamotorsports.com/DEX/

    Also, although nobody knows for sure, the failure mode of our Northstar engine gaskets "may" be in part due to Dex-Cool becoming acidic over time. From what I have read on this message board, one of the more likely theoretical failure sequences could work something like this:

    Step 1: the head gasket begins to slightly leak such that coolant makes its way to the head bolts

    Step 2: the Dex-Cool is now exposed to air and quickly becomes highly acidic

    Step 3: the head bolts start to become loose as the acidic Dex-Cool reacts with the aluminum block and dissolves the aluminum threads in the block

    Step 4: combustion pressure places enough force on the bolts that they pull loose from the block due to the weak threads damaged by the Dex-Cool


    Why does this happen with Dex-Cool? It appears that the addition of a specific organic chemical called 2-ethyl-hexanoic acid may be a big part of the root cause. As far as I can tell, ONLY GM and ONLY Dex-Cool (and Dex-Cool clones) use this organic acid in the design of the coolant. Ford tested Dex-Cool in one of its vehicles and decided NOT to use Dex-Cool, instead moving toward a Hybrid coolant containing organic additives (but not 2-ethyl-hexanoic acid) while still containing low levels of silicates (like the old green coolants had). A good primer on the various coolant options can be found here:

    .pdf
    http://www.gates.com/downloads/downl...older=brochure

    or .html

    http://findarticles.com/p/articles/m...g=content;col1

    I realize that some people are die-hard Dex-Cool supporters and others either want to know what their options are (besides Dex-Cool) and/or would like to switch from Dex-Cool to some other coolant which may avoid some of the issues with Dex-Cool. I do not want to start a "flame war" but rather have a meaningful dialog about options besides Dex-Cool for those of us who are interested.

    One of the best coolant cross reference matrixes I've found so far is here:

    http://www.eetcorp.com/antifreeze/Coolants_matrix.pdf

    This .pdf is also attached to this post.

    From my research, for anyone who wants to convert from Dex-Cool or a Dex-Cool clone and who also wants to avoid the 2-ethyl-hexanoic acid, I think there are a few options: Zerex G05 (does contain some silicates as well as borates), Peak Global (does not contain silicates, phosphates or borates), Motorcraft Orange (G05 clone), Honda Blue (contains phosphates by no silicates or borates). There may be others as well.

    For myself, I've converted one of my two Northstar powered vehicles over to G05 and I may use Peak Global in the other . . .

    Andrew
    Attached Files

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    Re: Thoughts on Dex-Cool and Head Gaskets

    Apparently DexCool can become acidic over time if it is either a) not maintained, or b) exposed to air due to minor leaks in the coolant system. Over time, the acidity of the Dex-Cool can damage all kinds of gaskets.
    Internet myth. How do you get it from the bottle to the engine without exposing it to air? And if this was true, how come all the other gaskets don't fail? How come all the other GM engine don't have HG problems?

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    Re: Thoughts on Dex-Cool and Head Gaskets

    OMG.....................




    .............and how come every other car in the world, most of which run DEXCOOL or a proprietary variant, don't "eat" gaskets.

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    Re: Thoughts on Dex-Cool and Head Gaskets

    Hi Ranger -

    I don't have all the answers and this was part of the reason for my post, to get feedback from others. Perhaps exposure to air is not the reason Dex-Cool becomes acidic, I really don't know . . . Perhaps it becomes acidic just due to a lack of maintenance. Either way, it still begs the questions:

    1. Why take the "chance" with Dex-Cool when other options are available?
    2. What causes the aluminum block to deteriorate and "let go" of the head bolts?
    3. Do we believe that the ONLY coolant option that will work in an aluminum Northstar is DexCool and if not, then why not change to something with a potentially lower risk of causing issues?

    It seems to me that earlier Northstars running on traditional green silicated coolant appear to have a much lower HG failure rate (based on survey on this site and comments from people doing these repairs), so why not switch to something more like that and try to reduce the risk of the HG failure?

    Andrew

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    Re: Thoughts on Dex-Cool and Head Gaskets

    The shift to DEXCOOL began in 1996. I think the failure rate for 97-98-99 is highest in the poll. We are of the opinion that the main problem is metallurgy - casting porosities in the block contributing to weak thread machining. Many pictures and posts earlier in here by AJxtcman on just this subject. Block casting changed in 2000.

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    Re: Thoughts on Dex-Cool and Head Gaskets

    Submariner409 -

    Perhaps I am beating the proverbial "dead horse" here, I hope not, and again, the goal is really to focus on options available to those who may want to switch versus having a debate over whether one should or should not switch. I have had a lot of trouble researching what non-Dex options were available and which ones would be compatible with an existing Dex fill without causing strange reactions, etc. I've only identified a few long life coolants that seem viable and I've already mentioned them.

    By the way from my research, very few (if any) other manufacturers beyond GM have adopted DEX or DEX equivalents as their recommended fill. From my research it appears that Daimler, Chrysler, Ford, BMW, Honda and Toyota do not use Dex. I am NOT a coolant expert so I can not guarantee this information is 100% correct, but I do believe it is . . .

    Andrew

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    Re: Thoughts on Dex-Cool and Head Gaskets

    Quote Originally Posted by submariner409 View Post
    The shift to DEXCOOL began in 1996. I think the failure rate for 97-98-99 is highest in the poll. We are of the opinion that the main problem is metallurgy - casting porosities in the block contributing to weak thread machining. Many pictures and posts earlier in here by AJxtcman on just this subject. Block casting changed in 2000.
    Hi Submariner409,

    Yes, this is another operating hypothesis which may very well be the case. Having said that, it seems very coincidental to me that the majority of issues occurred starting the years that DEX was first deployed. I realized that DEX cut-over initiated in '96 but I thought factory fill in '96 Northstars was still the traditional green silicated coolant? I also realize that many have described how often times the bolts that "let go" also are wet and the holes/threads badly corroded. If the issue was casting/porosity on its own then wouldn't all of the bolts be affected? And, why do the bolt holes get so badly corroded when the coolant gets to them?

    This is clearly a very complicated problem without a single variable causing the failure modes, it may possibly be compounded by many variables interacting in a unique way, as is often said to be the case with catastrophic engineering failures. In some cases, taking just one link out of the chain of events can eliminate (or greatly reduce) the risk of the failure occurring . . .

    Regards,

    Andrew

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    Re: Thoughts on Dex-Cool and Head Gaskets

    My wife is driving a '96 Bonneville 3800. It's 13 years old and has 160K on it and has never had a leaky gasket. So much for the Dex eating gaskets theory. By the way, Dex is acid based. That is probably what started THAT myth. Don't ask. I don't know what that means, but I am quite sure it is not anything that eats gaskets. Remember, you eat oranges and they have "acid" in them. There is no reason that you MUST use Dex. Use whatever tickles your fancy it you are uncomfortable with it. Using a different coolant will not cause any problems.

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    Re: Thoughts on Dex-Cool and Head Gaskets

    Quote Originally Posted by Ranger View Post
    My wife is driving a '96 Bonneville 3800. It's 13 years old and has 160K on it and has never had a leaky gasket. So much for the Dex eating gaskets theory. By the way, Dex is acid based. That is probably what started THAT myth. Don't ask. I don't know what that means, but I am quite sure it is not anything that eats gaskets. Remember, you eat oranges and they have "acid" in them. There is no reason that you MUST use Dex. Use whatever tickles your fancy it you are uncomfortable with it. Using a different coolant will not cause any problems.
    Hi Ranger -

    Thanks for the input. I think eventually all coolants deteriorate and become less basic. I've read that some coolants start with a pH in the 10-11 range and others start more in the 8-9 range. The high pH is said to be bad for certain metals - too basic. The lower pH coolants (like DexCool I think) are said to be better for some metals (like aluminum) however, the big issue is how well buffered the coolant is to preserve the basic nature of the coolant. If the pH crosses the neutral mark and goes acidic (due to the buffers breaking down), then the problems may begin in earnest, apparently including damage to nylon gaskets.

    I realize that many people have never had a problem with DexCool and the percentage with the issue varies. It does seem however that DexCool may have more very serious issues than other products available . . .

    Which non-Dex coolant do you recommend for aluminum engines like the Northstar?

    Regards,

    Andrew

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    Re: Thoughts on Dex-Cool and Head Gaskets

    Any old standard green Ethylene Glycol-based coolant advertised as being low-silicate formula or no-silicate formula. Havoline or Prestone in a 60/40 coolant/distilled water mix.

    Stop being a chemist and drive your car. Trying to suss out the various coolant chemistries and how they react over time with various metals may lose you some sleep but it won't solve anything in the engine. Or are you an organic chemist with DuPont ???

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    Re: Thoughts on Dex-Cool and Head Gaskets

    The coolant additives are what deteriorate and need replenishment.

    I have no recommendations as I don't know anything about them. I seem to recall someone touting G05, but I can't recall who or why. Personally I think it is like oil. People have their favorites, swear by one and at the other, but in the end all that matters is that it gets changed.

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    Re: Thoughts on Dex-Cool and Head Gaskets

    The information below might or might not be useful to this discussion. I don't have a dog in this hunt and I don't have a chemistry degree.

    What I am is the daily driver of a properly maintained high mileage '98 Seville.

    The following was pulled from the Chevron/Texaco web site three or four years ago.

    * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

    Havoline® Extended Life Anti-Freeze/Coolant DEX-COOL®
    Detailed Product Specifications

    Havoline Extended Life Anti-Freeze/Coolant DEX-COOL is a
    single-phase, ethylene glycol type universal automotive engine
    coolant based on a Texaco's patented long life organic corrosion
    inhibitor system.

    Havoline Extended Life Anti-Freeze/Coolant Pre-Mixed 50/50 DEX-COOL
    is a 50/50 mixture of Havoline Extended Life Anti-Freeze DEX-COOL
    with deionized water.

    Havoline Extended Life Anti-Freeze/Coolant DEX-COOL is a universal
    engine coolant that incorporates patented organic acid corrosion
    inhibitor technology. This coolant meets both ASTM D 3306 for
    automotive service and ASTM D 4985 for heavy-duty diesel service. It
    is a nitrite-, nitrate-, phosphate-, silicate-, borate and
    amine-free formulation which uses Texaco’s patented carboxylate
    technology to provide maximum protection of the six basic metal
    alloys found in most heat transfer systems. Since the coolant
    contains no phosphates or silicates, hard water deposits in the
    cooling system are almost eliminated. The low level of abrasive
    dissolved solids in Havoline Extended Life Anti-Freeze/Coolant
    DEX-COOL results in improved water pump seal life.

    The life of a coolant in an automobile engine is limited by the
    corrosion protection ability of the corrosion inhibitors. The main
    corrosion inhibitors in Havoline Extended Life Anti-Freeze/Coolant
    DEX-COOL have been shown to remain above 95% of their original
    concentration after 150,000 miles in automobiles.

    This allows much longer intervals between coolant changes without
    worrying about loss of corrosion protection. Used Havoline Extended
    Life Anti-Freeze/Coolant DEX-COOL was tested in laboratory
    controlled corrosion tests for new coolants after it had already
    been in service for more than 200,000 miles.

    The used Havoline Extended Life Anti-Freeze/Coolant DEX-COOL passed
    the ASTM D 1384 requirements for glassware corrosion with results
    equivalent to new coolants and also passed the ASTM D 4340 Aluminum
    Hot Surface Test for new coolant. Havoline Extended Life
    Anti-Freeze/Coolant DEXCOOL represents the next generation of
    universal engine coolants.

    This coolant is suitable for a five year or 150,000 miles service
    life in automotive applications. Note: These products are not to be
    used to protect the inside of potable water systems against freezing.

    Havoline Extended Life Anti-Freeze/Coolant DEX-COOL is manufactured
    from ethylene glycol and a highly effective long term corrosion
    inhibitor package based on carboxylate technology. This inhibitor
    system eliminates the need for
    silicates, phosphates, borates, nitrites, nitrates and amine
    additives traditionally used for this purpose. The replacement of
    these inhibitors is significant for water pump life because many of
    these conventional inhibitors have been shown to be abrasive to
    water pump seals. In comparison field tests with conventional
    coolants in taxi fleets, Havoline Extended Life Anti-Freeze /
    Coolant DEX-COOL significantly reduced the need to replace water
    pumps during the 100,000 mile test.

    In addition to fleet tests, this product has also been tested by a
    major manufacturer of water pump seals, and has been found to be
    more compatible with the seals than any other coolant tested.
    Benefits:
    Meets GM 6277M--GM’s new Long Life Coolant specification
    5 year or 150,000 mile service interval
    Provides effective, long term corrosion protection for aluminum,
    brass, cast iron, steel, solder and copper
    Protects against winter freeze up and minimizes the chance of
    summer boil over
    Compatible with water pump seal materials and minimizes the
    formation of abrasive dissolved solids
    Storage stable for at least eight years
    No silicate dropout or gel formation during use or storage
    100% biodegradable in its pure unused form
    Excellent heat transfer properties
    Nitrite-, borate-, phosphate-, nitrate- and amine-free
    Outstanding hot surface aluminum protection
    Superior protection in high operating temperatures
    Compatible with conventional antifreeze. Dilution with
    conventional antifreeze will reduce extended life benefits.

    ChevronTexaco recommends that this product not be diluted by more
    than 10% with conventional coolants.


    © 2003-2005 ChevronTexaco Corp. All rights reserved

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    Re: Thoughts on Dex-Cool and Head Gaskets

    BINGO !!!

    If you highlight the "Havoline Extended Life..................." line (Firefox) and right-click on the highlight you can call up the Google search for the article.

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    Re: Thoughts on Dex-Cool and Head Gaskets

    Learn something new every day.

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    Re: Thoughts on Dex-Cool and Head Gaskets

    I'm not really seeing anything I wasn't already aware of in that description. Although there are some technical specs provided, they are not comprehensive as they do not really detail what IS in the mix . . . Also, I noticed that the test results were "lab" based and not "real world" based. Unfortunately, the lab often doesn't represent reality . . .

    Thanks for sharing this though - first time I'd seen it.

    Andrew

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