Headgaskets - deterioration or pulled head studs?
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Northstar Engines and System Technical Discussion Discussion, Headgaskets - deterioration or pulled head studs? in Cadillac Engine Technical Discussion; This whole headgasket problem with the Northstar engine has really piqued my curiousity. There's probably two different reasons for that ...
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    djb25 is offline Cadillac Owners Member
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    Headgaskets - deterioration or pulled head studs?

    This whole headgasket problem with the Northstar engine has really piqued my curiousity. There's probably two different reasons for that - one is that I just purchased a '99 STS with 86k, and I'd rather not have to pull the heads, and the other is that I've had quite a bit of experience with Porsche 911's, which had similar headstud pulling/breaking issues (which, for obvious reasons, were not related to coolant changes or head gasket problems).

    My question is basically whether there are two problems cropping up - headstuds have a tendency to pull out of the block and headgaskets are deteriorating when the coolant isn't properly maintained, or whether these problems are intimately related somehow (and not independent of each other).

    The Porsche angle comes from the late '70s versions of the 911, which were basically magnesium blocked engines with aluminum heads. The headstuds (made of steel) tended to pull themselves out of the block due to the dramatically different thermal expansion rates of the two metals. The problem was exacerbated by the tendency of the engines to run very hot, due to the massive amounts of early emission-reduction "technology" on the engine. The solution was (suprise!) to replace the head studs and timesert the block. The problem was permanently cured in the 911SC, when Porsche went to a full aluminum block with aluminum heads. As such, I'm a little surprised to see a similar problem popping up in the Northstars, and the cause being attributed to the aluminum block. It sounds to me like the problem is really a design flaw, in that the engineers didn't properly account for the strength needed to keep the heads on the engine and the studs in their place, and not an inherent weakness in the use of aluminum in teh construction of an engine block. There are a lot of aluminum engines out there that do not exhibit these problems.

    Lastly, I noticed that there has been some allegations as to poor quality headgaskets being used in a few years of the Northstar construction, and that also sounds like a pretty reasonable explanation for the headgasket deterioration. Regular coolant changes are certainly necessary for the longevity of any engine, but if there are problems popping up in cars with under 75k miles, when the coolant is rated for 100k miles between changes, I can't help but think there may be something more to the problem than old coolant. I'd love to have access to the data on these headgasket failures, and see how many occurred on cars without perfect maintenance of the coolant system compared to cars that were maintained properly.

    Anyway, these are just some observations I've made as a newcomer to this forum and Cadillac ownership in general.

    - Damion

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    Re: Headgaskets - deterioration or pulled head studs?

    Quote Originally Posted by djb25 View Post
    This whole headgasket problem with the Northstar engine has really piqued my curiousity. There's probably two different reasons for that - one is that I just purchased a '99 STS with 86k, and I'd rather not have to pull the heads, and the other is that I've had quite a bit of experience with Porsche 911's, which had similar headstud pulling/breaking issues (which, for obvious reasons, were not related to coolant changes or head gasket problems).

    My question is basically whether there are two problems cropping up - headstuds have a tendency to pull out of the block and headgaskets are deteriorating when the coolant isn't properly maintained, or whether these problems are intimately related somehow (and not independent of each other).

    The Porsche angle comes from the late '70s versions of the 911, which were basically magnesium blocked engines with aluminum heads. The headstuds (made of steel) tended to pull themselves out of the block due to the dramatically different thermal expansion rates of the two metals. The problem was exacerbated by the tendency of the engines to run very hot, due to the massive amounts of early emission-reduction "technology" on the engine. The solution was (suprise!) to replace the head studs and timesert the block. The problem was permanently cured in the 911SC, when Porsche went to a full aluminum block with aluminum heads. As such, I'm a little surprised to see a similar problem popping up in the Northstars, and the cause being attributed to the aluminum block. It sounds to me like the problem is really a design flaw, in that the engineers didn't properly account for the strength needed to keep the heads on the engine and the studs in their place, and not an inherent weakness in the use of aluminum in teh construction of an engine block. There are a lot of aluminum engines out there that do not exhibit these problems.

    Lastly, I noticed that there has been some allegations as to poor quality headgaskets being used in a few years of the Northstar construction, and that also sounds like a pretty reasonable explanation for the headgasket deterioration. Regular coolant changes are certainly necessary for the longevity of any engine, but if there are problems popping up in cars with under 75k miles, when the coolant is rated for 100k miles between changes, I can't help but think there may be something more to the problem than old coolant. I'd love to have access to the data on these headgasket failures, and see how many occurred on cars without perfect maintenance of the coolant system compared to cars that were maintained properly.

    Anyway, these are just some observations I've made as a newcomer to this forum and Cadillac ownership in general. Anyway, these are just some observations I've made as a newcomer to this forum and Cadillac ownership in general

    - Damion


    Hello new member. Here is a thread that contains alot of info that deals with HG'. It's really a battle
    and in the mist of the battle alot of info comes trinkling out. Regardless I thought you might want to read more info on the subject.

    http://www.cadillacforums.com/forums...light=Bluemoon

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    xxcaddytech is offline Cadillac Owners Member
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    Re: Headgaskets - deterioration or pulled head studs?

    ok here's the skinny from someone who has done ALOT on n* (1st in atlanta to tear into one in 93) 99% are block/thread failures which causes the gaskets to burn and look like the culprit. went over this with the engineers back when the had us heli-coiling instead of timeserts..overheating seems to be a for sure thread killer. the blocks are not made of great material not dense enoughthats why the ls1-ls6 blocks are made of a stronger aluminum now. unsure if the n* changed to the new material also it is a dull grey instead of a shiney silver...

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    Re: Headgaskets - deterioration or pulled head studs?

    DJB and XXXCAD

    The practical and technical experience you both have on this subject is very valuable to persons on the forum trying to understand. Keep posting.


    I don't know the truth on the head gasket / head bolt issue.

    There are glimmers of what could have been going on in engineering. consider the following.

    Another mfg not GM was concerned about paying out Engine replacement
    warranties on auto w less than 50,000 miles. Blamed gasket mfg. Think of it
    a 5,000 $$ replacement blamed on a 5.00 gasket.. Gasket mfg said NO it is not our fault. Scientific investigation revealed the following.

    hose at water pump was sucking in air and no coolant was observed leaking at hose. Air in the system was the culprit. The fix was to put two clamps on each end of water pump hose. Early Warranty claims stopped.

    The variation on the above for N* and other GM engines is the lower hose has a spring inside that will rust and break and allows caviatation to collapse the hose momentarily. Scenario is set for heat stress. When mfg states that failure is due to Owner Neglect of cooling system they do not get specific it is always so vague.

    The cost to protect from hose collapse is probably .25 more for stainless steel spring vs. steel will rust.

    XXCAD can you remember where the head gasket would burn? Same location? I have wondering why I never see a post/picture of bad N* gaskets.

    DJB did you ever see a Porsche engine w head studs instead of headbolts?

    regards

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    Re: Headgaskets - deterioration or pulled head studs?

    How is a steel spring going to rust if the coolant has corrosion inhibiters in it (assuming that the coolant is changed when it is supposed to be).

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    Re: Headgaskets - deterioration or pulled head studs?

    Ranger you are right on. "How is a steel spring going to rust assuming the coolant has been changed. " Time after time we have heard that engine was damaged because owner/operator failed to change coolant in timely fashion. The coolant still cooled , the ethylene glycol still prevented freezing it did not wear out. So what component does the mfg point to that gave up? RUST inhibitors.

    If you leave the old coolant in too long you deprive system of rust protectection. But what part does a high tech Alum alloy engine have to do w ferous oxide. I don't pretend to know the complete story however when that thermostat opens up it wants to suck that hose collaped, sometimes the steel spring is weak and momentary hose collapse shuts off flow of coolant that is in dire need. Springs that do break will NOT be covered in rust it only requires a few specs of rust and then the constant contraction brought on by open/close of thermostat. SNAP.

    Another part of rusting steel in a high tech ALUM engine is the zinc plated
    "core plug" that I just have call a freeze plug. You may have seen the picture posted on this forum showing a N* eng on floor , pulled for H G Time sert job. They replaced the plug and reinstalled the engine.. I applaud.

    Two small parts, 2.00 total that threaten an excellent 8500.00+ engine.

    How can we cope w little things that threaten in a large manner.

    As we read/write these things realize that GM has 100,000 mile coolant and will at least double the auto warranty, plus they possibly will change direction of coolant flow on N* RWD.

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    Re: Headgaskets - deterioration or pulled head studs?

    yes, corrosion inhibitors wear out or get used up. That is the reason we have to change coolant. If you don't, the head gaskets corrode from the inside. That is the most common cause as I understand it. Now that is not to say that a well maintained engine has never suffered a head gasket failure.

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    xxcaddytech is offline Cadillac Owners Member
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    Re: Headgaskets - deterioration or pulled head studs?

    no specific spot that is prone to burn first it just depends on which thread in the block gave out first remember with the extreame heat and pressure generated in the combustion chamber .001 of an inch can mean failure or not. and with the thearmal expantion rates of aluminum being what they are. things move around alot more tham most think. i will look at my 05 and see if they changed the block material. they did it on the ls1-6 motors starting in 02. 25% of the f-bodys had the new block material..let us pray they did the same for us...

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    Re: Headgaskets - deterioration or pulled head studs?

    This is very interesting considering the fact that something as little as a clamp could cause such a big problem.

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    Re: Headgaskets - deterioration or pulled head studs?

    I think that any modern alloy engine will be prone to damage if the slightest loss of water/coolant is not stopped and leaks sorted out immediatley.
    The N* it seems is no different.
    I am just amazed that an engine like this is actually no better than a common or garden Citroen or Vauxhall engine.
    My 99 STS N* engine has only done 75K and has the HGs gone.
    I am slightly dissapointed but know now that coolant levels are an absolute essential item........far greater it seems than changing oil at 3K as the service manuals state.
    There is no doubt that the slightest leak of coolant or problem with your cooling system could cause a blown gasket. This I now know to my detriment but then I also know that this is not unusual in any modern alloy engines.

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    Re: Headgaskets - deterioration or pulled head studs?

    Quote Originally Posted by C170B View Post
    DJB and XXXCAD

    DJB did you ever see a Porsche engine w head studs instead of headbolts?

    regards
    Actually, I've never even heard of a porsche engine with head bolts - I know the 911s, 944s, and 928s all use studs.

    Personally, I would think studs would be a more reasonable way to go with an aluminum engine, less chances of cross-threading and damage. I was very surprised when I heard the N* used bolts.

    - Damion

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    Re: Headgaskets - deterioration or pulled head studs?

    It's noteworthy to reflect that Rolls-Royce addressed the problem in their V1650 Merlin by, at one point, casting the heads and cylinder blocks in one piece and assembling the engine through the bottom instead of through the top..

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    Re: Headgaskets - deterioration or pulled head studs?

    Quote Originally Posted by djb25 View Post
    Actually, I've never even heard of a porsche engine with head bolts - I know the 911s, 944s, and 928s all use studs.

    Personally, I would think studs would be a more reasonable way to go with an aluminum engine, less chances of cross-threading and damage. I was very surprised when I heard the N* used bolts.

    - Damion
    I worked on a Porsche 1600 normal about 45 years ago and if memory serves me correctly it had a combination of bolts and studs.

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    Re: Headgaskets - deterioration or pulled head studs?

    Quote Originally Posted by dkozloski View Post
    I worked on a Porsche 1600 normal about 45 years ago and if memory serves me correctly it had a combination of bolts and studs.
    1600 Normal? That's a VW engine!

    j/k - everyone knows that the only "real" porsches have push-rods!

    - Damion

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    Re: Headgaskets - deterioration or pulled head studs?

    Quote Originally Posted by djb25 View Post
    1600 Normal? That's a VW engine!

    j/k - everyone knows that the only "real" porsches have push-rods!

    - Damion
    The car was a 1956 Porsche It had four cylinders and said 1600 across the engine lid. I was working on it because the camshaft gear was made of micarta and all the teeth were torn off of it. We went to the Volkswagon/Porsche dealer to get a new gear and were told that we had to buy a new cam and all for $800. We opted for an alloy cam gear for a Volkswagon for $14 and it worked just fine. The guy that owned the car was a Porsche fanatic and was thoroughly mortified when he found out what we had done.

    http://www.cadillacforums.com/forums...1&d=1157941369

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