Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!
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Cadillac Seville / Cadillac Eldorado Forum Discussion, Head bolts!!!!!!!!!!!!!!!!!!!!!!!!! in Past Cadillac Vehicle Discussion; ...
  1. #1
    jvf1095 is offline Cadillac Owners Fanatic
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    Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    Hello All….

    I have a question that’s been asked many times on this forum & elsewhere; & I’ve read every post or tech write up here & elsewhere (or as many as I can find at least). But I want to ask it and approach it in a different way. What EXACTLY causes the head bolts to pull away in the Northstar engine?

    Scenario 1…A new 98 Eldorado is purchased. The car is in a garage, never driven. In fact, no Dexcool in it no other fluids. The car is just a show piece with no intention of EVER being driven or started up. My assumption with this car is that the bolts/threads will never corrode or pull away because the car is static. No fluids, never run. (Yes, no)?

    Scenario 2… Same car. Hardly driven, say 1,000 miles a year. Not driven “hard”, no excessive torque or strain on the engine, Dexcool changed every 2 years (every 2,000 miles). Will the head bolts eventually start to corrode & pull away because of age & not mileage? Will vibration eventually loosen them because the threads are not course or long enough? Are the heads porous (which I read) where as the Dexcool will eventually seep into the threads & cause them to corrode & pull away, even with fresh Dexcool that has not been “chemically altered” or “gone bad” because it’s old & was never changed?

    Even in Scenario 1, will they eventually start to corrode simply because of an interaction between the metal composition of the bolts, vs the metal composition of the heads?

    If the car never overheats will they never corrode or pull away because there is no undo strain or excessive heat or warping of the heads? Or in plain English… What the flying @#$%&^# is it that “gets to these bolts” or causes these bolts to corrode that will make them start to pull away? Thanks!!! Joe

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it.
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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    The Engines; Northstar forum ..............

    Please read the several threads (stickies) on the subject in Engines; Northstar. It has all been covered and discussed to death since 2002 (the forum start date).

    Google "cadillac forums northstar head bolt hole thread failure".

    Vibration, heat, overheats, degree of use, and properly maintained DEX-COOL apparently have nothing to do with the problem

    You'll need a bourbon and water.

    (For your engine it's probably the block metallurgy - which, along with other mechanical modifications, changed significantly for the 2000 and later engines.)(The Engines; Northstar stickies.) Get into the block porosity discussions.

  4. #3
    jvf1095 is offline Cadillac Owners Fanatic
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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    Or a bottle of Johnny Walker Black!!!

  5. #4
    jvf1095 is offline Cadillac Owners Fanatic
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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    Submariner..... I read through some of the block porosity issues, versus other things that may not affect the head bolts as you indicated in your post below. If so, I'm thinking if I had a porous block it would have caused a problem by now since the car is 21 years old (only 27,000 miles on it), and that's more than enough time for the Dexcool to get to the bolts via a "spongy block?" So given that, maybe I'm in the clear as far as my Northstar goes? Any opinions on that? Thanks guys.

  6. #5
    basscatt's Avatar
    basscatt is offline Master of the Dark Art of Diagnostics
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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    What EXACTLY causes the head bolts to pull away in the Northstar engine?
    several things affected the problem -

    GM started with a short - fine thread head bolt - which was OK - at first -

    the aluminum alloy was changed sometime after 1995 to a softer/weaker/probably cheaper alloy -

    the procedure for casting the block also changed around the same time -
    creating a more porous block -

    partial success came in 2000 with the longer head bolts - but still had the fine threads -

    final success came in mid 2004 - when GM went to a long bolt with coarse threads -

    --------------------
    the bottom line is that the short fine-threaded bolts tore the threads out of the soft/porous aluminum block -

    once the head bolt holes were drilled/tapped and large inserts were installed -
    the engine was permanently repaired -

    and VERY few 2004+ Northstar motors with the long/coarse-thread bolts ever has the head bolt problem -

    HOWEVER - ANY ENGINE can develop head gasket failure for "no apparent" reason -

    ---------------------------

    Scenario 1.........................
    My assumption with this car is that the bolts/threads will never corrode or pull away
    because the car is static. No fluids, never run. (Yes, no)?

    possibly - but - how would you ever find out?

    Scenario 2…........................
    the ONLY correct answer for ALL your questions is - MAYBE -

    the actual failure rate was around 10% -
    of these some were meticulously maintained -
    others never had the coolant - or anything else changed -

    the reason it became such a big deal is the expense to fix the problem -
    dealers were charging $6000+
    keep in mind that this is a forum where people come to solve problems -

    you never hear people come here to post
    "my car has 100,000 miles and I have never had a single problem"

    --------------------------

    lastly - pulled head bolts aren't the biggest/most common/most expensive problem with these cars -

    if your Eldo has the F45 - electronic suspension system -
    be sore you are sitting down when looking for new struts and shocks -
    $750 - EACH - if you can even find ANY - and that doesn't include the labor -

    another biggie - the DTC P0741 -
    a simple worn out seal - buried $2500 deep in the trans -

    ------------------------

    remember these two sayings:
    1) old Cadillacs are cheap to buy - and very expensive to drive -

    2) only the rich can afford to own/drive an old Cadillac -

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    Ranger's Avatar
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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    Did you read the "Root Cause" sticky in the Northstar forum?
    https://www.cadillacforums.com/forum...ilure-fix.html

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    jvf1095 is offline Cadillac Owners Fanatic
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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    Basscatt, thanks for the info, especially the F45 option. Going to check the build sheet that came with the car. Hope I don't have it! Ranger, if the "Root Cause Sticky" is what you attached below, then yes I read it. With that, regarding the porous issue, what I want to know (if there is an answer to my question) is this..... Given that the heads in my 98 Eldo might be porous (that is, if they are), wouldn't the Dexcool have "soaked" through the porous aluminum by now given that the car is 21 years old? Given that, I'm figuring it should have happened by now? So I'm hoping that if it hasn't happened by now, I might be ok? Thanks!! Joe

  9. #8
    Harry Yarnell is offline Cadillac Owners Connoisseur
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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    If it 'aint broke, don't fix it.

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    jvf1095 is offline Cadillac Owners Fanatic
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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    Hello Harry. I agree, Don't want to fix anything, especially if there isn't a problem at this point. But just want to know if my "theory" makes any sense in that, if my aluminum head were porous, the Dexcool would have seeped into the head bolts by now given it had 21 years to do so. (By the way, my 98 Eldo has only 27,000 miles on it).

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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    Remember - the Northstar System engine was designed and tested to run for 50 miles with NO coolant - Camel Mode.

    It wasn't the heads - they're damned tough and won't warp even under some hellish overheats. It was the cylinder block aluminum alloy castings = weak bolt hole threads.

    Head bolt(s) loosen, gas escapes past the gasket fire ring at the iron cylinder liner, eats the soft gasket material, enters the cooling system thus over-pressurizing it, blows off coolant, water pump loses flow, the engine overheats.
    Attached Images

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    jvf1095 is offline Cadillac Owners Fanatic
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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    Hello Sub! So it's the cylinder block casting that might be porous, which in turn can cause the Dexcool to seep into the bolt holes & corrode the threads, thus causing the bolts to pull away & not the heads? Ok, so if that's the case, & if the porous issue is the main reason why Dexcool would eventually seep into the bolt holes via the block, there's a good chance I might have dodged the bullet with my 98 Eldo? I know nothing is guaranteed in life but death & taxes, but I'm hoping that the odds are in my favor because given the car is 21 years old, that's enough time for a porous block to allow Dexcool seepage to get at the bolts? Thanks guys, I know there's nothing I can do to stop anything from happening, but given my specifics (age of the car, 27K miles), I guess I'm just trying to understand it more & hoping that I hopefully "escaped" this issue. Also, I know one thing has nothing to do with the other, but I've had this car for 1 1/2 years. The car doesn't leak oil, & I've never had to add oil between oil changes, so it doesn't seem to burn oil either. Just wanted opinions based on all this if you experts feel I'm more in the "green" on the meter with this possible bolt pull away issue as opposed the "yellow or red?" Thanks!!!

  13. #12
    Submariner409's Avatar
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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    DEX-COOL is a perfectly satisfactory coolant - like many others - when properly maintained as recommended by the manufacturer.

    My 2002 has run it since Day One, properly maintained, changed ever 3 - 4 years, and the cooling system metal is shiny and squeaky clean.

    One school of thought is that, because DEX-COOL in a long-life coolant - and most daily driver owners believe that a Cadillac requires no maintenance - the stuff is left in the system too long, turns acid, and accelerates block porosity problems. ANY coolant can do that.

    BUT, go way, way back in the Northstar stickies and find AJXTCMAN's pictures of casting ash pits in Northstar block head bolt holes.

    You haven't dodged anything - if the engine is going to shit a head bolt, it will - and you can do nothing to stop it short of very costly "preventive maintenance".

    If it ain't broke, don't fix it.

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    jvf1095 is offline Cadillac Owners Fanatic
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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    Thanks Sub. I'll take a look. From what I've gathered here, I'll spend money on changing my Dexcool every two years regardless of mileage or what it costs because I'll do it myself. Yeah, might seem like overkill, BUT, if fresh Dexcool (as opposed to that which might turn) will lessen the chance of this happening; especially given these Northstar blocks are prone to be porous, then to me it's worth a few bucks for some piece of mind. Tell me though Sub, if fresh Dexcool (as opposed to Dexcool that has turned acidly) gets to the bolts; will that cause a problem too? Lastly, anyone that thinks a Caddy or any other high end car does not require proper maintenance is a fool. I'd rather overkill the maintenance any time, than not!

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    Submariner409's Avatar
    Submariner409 is offline If it won't run, chrome it.
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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    Remember: The very act of owning and driving a car causes things to wear out, leak, and break - and we can do nothing to change that.

    I (and no other forum member that I know of) has any idea or chemical analysis of whether new or old DEX-COOL can/will/might/could cause any sort of failure acceleration rates.

    Take car of the car, keep it clean, and drive it (like you stole it (occasionally)).

    Have you studied all of this? It was written by one of the GM Northstar Powertrain engineers and applies mainly to the pre-2000 engines.

    https://www.cadillacforums.com/cadillac-tech.html

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    jvf1095 is offline Cadillac Owners Fanatic
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    Re: Head bolts!!!!!!!!!!!!!!!!!!!!!!!!!

    I'll look at that as well; & I do understand what you are saying. Maintenance & staying on top of it as best as possible has always been something I do religiously; especially with a car like this. Even bought a Block Tester & have checked it every month given what I've learned on this forum about possible Northstar issues & what I will continue to learn here. So outside of that & learning all I can; I realize it's a crap shoot & luck of the draw. Thanks guys; & best of luck to all of you with your respective cars. Like Sub said, take car of em, but drive em like you stole em too!

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