So how many people have had overheating/bad head gasket problems?
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Northstar Engines and System Technical Discussion Discussion, So how many people have had overheating/bad head gasket problems? in Cadillac Engine Technical Discussion; It seems like this is an epidemic. Somewhat high mileage Northstars.. over heating due to bad head gaskets. Especially 93-95 ...
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    JAvery20 is offline Cadillac Owners Member
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    So how many people have had overheating/bad head gasket problems?

    It seems like this is an epidemic. Somewhat high mileage Northstars.. over heating due to bad head gaskets. Especially 93-95 years. Im just wondering how many people on the forum have had this problem. Ive run into quite a few around town and have read about quite a few on the various forums.

    Im actually picking my car up tomorrow from its head gasket repair. :rolleyes2 Its a 93 ETC btw.

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    fristim is offline Cadillac Owners Fanatic
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    Re: So how many people have had overheating/bad head gasket problems?

    Quote Originally Posted by JAvery20
    It seems like this is an epidemic. Somewhat high mileage Northstars.. over heating due to bad head gaskets. Especially 93-95 years. Im just wondering how many people on the forum have had this problem. Ive run into quite a few around town and have read about quite a few on the various forums.

    Im actually picking my car up tomorrow from its head gasket repair. :rolleyes2 Its a 93 ETC btw.

    I myself haven't had any head gasket problems but then agian I have a 98 concours. My question is how much did your fix cost you and who did you have do it?

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    JAvery20 is offline Cadillac Owners Member
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    Re: So how many people have had overheating/bad head gasket problems?

    well I took it to a few guys around town and they all told me it would be cheaper to just drop a new engine in. well that equates to i just dont wanna do headgaskets or im scared of that cadillac emblem. So i was looking at about 3 grand for a new engine or a new head gasket. Ive heard ppl quoted on the forums saying expect anywhere from 2500-4000 for my particlular problem.

    I thought that was a little crazy, since the engine only had 120k on it and ran like a champ. I was either going to run it into the ground or find somebody that would not screw me over and just do the head gasket. I eventually found somebody that quoted me 700 up front. He knew my dad and said he just did a head gasket on a northstar cadillac a week ago. So i was happy, and hopefully everything works out when i pick her up tomorrow.

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    Re: So how many people have had overheating/bad head gasket problems?

    ive got a 94 ETC and the only overheating problem ive had is due to a hole in the radiator but other than that it stays about 196 degree and is a strong engine

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    Anthony Cipriano is offline Cadillac Owners Fanatic
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    Re: So how many people have had overheating/bad head gasket problems?

    Quote Originally Posted by JAvery20
    It seems like this is an epidemic. Somewhat high mileage Northstars.. over heating due to bad head gaskets. Especially 93-95 years. Im just wondering how many people on the forum have had this problem. Ive run into quite a few around town and have read about quite a few on the various forums.

    Im actually picking my car up tomorrow from its head gasket repair. :rolleyes2 Its a 93 ETC btw.
    A couple of points. There are millions of Northstar engines on the road. Overall, very few of them have head gasket or overheating problems. Reading this forum will lead you to the conclusion that all Northstars blow head gaskets, use oil, leak oil, etcetera. That's the nature of internet forum. Read a Mercedes forum and you would think that their cars are junk. Same with Lexus. They "all" broke timing belts on that site. There's a BMW 750i hate site. "All" of those overheat, needed new blocks, etcetera. Get the idea? No one looks up or searches out a forum to brag about how good their car is. But everyone with a problem looks up the appropriate site to vent, bitch, commiserate, complain, etcetera. So all internet sites make the specific brand look like there is an epidemic of problems.

    There are quite a few 93, 94, 95 Northstars showing up with failed head gaskets the last few years. There is a reason. It's called lack of maintenance. The Northstar is an all aluminum engine. Any and every all alluminum engine is very susceptible to internal damage due to corrosion if the cooling system isn't maintained. The 93, 94, 95 Northstars, specifically, were factory filled with the conventional green, silicated coolant that specifically required replacement every 2-3 years/24-32,000 miles to keep the corrosion inhibitors in the coolant at the correct strength. If the coolant is left in the sytem too long the corrosion inhibitors become depleted (even though the coolant looks nice and green and "checks" good for temperature protection) and the engine and cooling system can corrode internally. This leads to failed head gaskets as the steel core of the laminated head gaskets will start to corrode from the edges at the coolant jackets and eventually just rot away from the inside out. Purely an issue of lack of maintenance by the previous owners.

    The Northstar is very easy to repair in this case as even stripped head bolt holes can be easily repaired with the correct Timesert thread repair inserts. It just takes a knowlegable mechanic with the proper tools and instruction. A factory shop manual is absolutely mandatory doing repairs to the engine as it does require special assembly and bolt tensioning techniques.

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    Re: So how many people have had overheating/bad head gasket problems?

    I have '98 model SLS with 55,000 miles.
    Over the past half year I noticed that the coolant needed to be refilled several times with about a liter every time. The workshop could not find any fault.
    Then in the beginning of February the heating suddenly disappeared an a few minutes later the engine temperature started to rise and fluctuate above the normal temperature to quickly travel close to the red. I stopped the car and the engine. A few minutes later, I started the engine again. Now the engine temperature quickly returned to almost normal. I drove to my garage after again having refilled the coolant, but now about a gallon. The garage again could not find anything wrong, not even after a 20-minute drive on the highway. No coolant was missing.
    I now drove home, but after 5 miles, the same behavior returned, with fluctuating indicator needle, heat disappeared. When getting home I checked the coolant, which again was low by about a gallon. I refilled and returned to the garage. This time they did find exhaust gases in the coolant.
    They believed it to be the head gasket(s).

    Removing the entire engine and transaxle assembly to get to the head gasket, it was discovered that one of the gaskets was half way perforated at one of the cylinders, but the metal sealant around the actual cylinder looked ok. The head-bolts were all tightly pulled.

    The conclusion was that the head gasket must have been bad quality, perhaps leaking for some long time. The care has not been driven hard.

    The entire procedure cost $5000 to get fixed, including replacement parts and coolant. This car has been meticulously taken care of. No scheduled maintenance skipped and all fluid levels regularly checked.

    Lack of maintenance was not the reason, but poor head gasket quality.

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    Re: So how many people have had overheating/bad head gasket problems?

    I'll have to agree. My 94 STS is down right right now for head gaskets. There is no (0) corrosion to the head gaskets or to any other part of the cooling system. The motor has 73K miles.

    On this motor the head bolts pulled right out of the block.

    Whether the car was over heated or not I don't know as I haven't owned it since new, but an overheat still should not cause the headbolts to pull out. It could cause the head gasket to compress enough to cause it to "collapse" from under the head. But still wouldn't explain the pulled/stripped head bolts.

    I beleive the problem to be the integrity of the block threads. Which, with out any manufacturing changes, or time-serts, could have been to a great extent prevented with studs for mounting the heads. Studs do not distress the block threads upon installation, thus retaining 100% of the integrity originally designed, and more. Simply put, they are much stonger.

    This being my impression of this particular engine. This is the only one I have diassembled. It is entirely possible I have a defective one. But IF the same failures are typical to the NS' s I would say they have a problem.

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    Re: So how many people have had overheating/bad head gasket problems?

    On the bolt problem, that Lawrence is writing about.
    I have heard from the workshop that the bolts today are of a kind, which are tightened not with specific torque, but instead a specific angle. These bolts are called tension-bolts. You get the intended force to hold down the top through the head gasket to the engine block through, as it were, a spring, although with restricted elasticity. Sometimes these bolts snap, usually were the thread is. In order to remove these, GM is said to have developed a special tool enabling the removal of that part without having to take off the top. That is supposing that the head gasket is not leaking.
    It seems that broken tension bolts is not that uncommon as witnessed here .
    A search for “tension bolt” using Google returns 1690 hits.

    My car did not have that problem though.

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    Re: So how many people have had overheating/bad head gasket problems?

    Quote Originally Posted by Anthony Cipriano
    A couple of points. There are millions of Northstar engines on the road. Overall, very few of them have head gasket or overheating problems. Reading this forum will lead you to the conclusion that all Northstars blow head gaskets, use oil, leak oil, etcetera. That's the nature of internet forum. Read a Mercedes forum and you would think that their cars are junk. Same with Lexus. They "all" broke timing belts on that site. There's a BMW 750i hate site. "All" of those overheat, needed new blocks, etcetera. Get the idea? No one looks up or searches out a forum to brag about how good their car is. But everyone with a problem looks up the appropriate site to vent, bitch, commiserate, complain, etcetera. So all internet sites make the specific brand look like there is an epidemic of problems.

    There are quite a few 93, 94, 95 Northstars showing up with failed head gaskets the last few years. There is a reason. It's called lack of maintenance. The Northstar is an all aluminum engine. Any and every all alluminum engine is very susceptible to internal damage due to corrosion if the cooling system isn't maintained. The 93, 94, 95 Northstars, specifically, were factory filled with the conventional green, silicated coolant that specifically required replacement every 2-3 years/24-32,000 miles to keep the corrosion inhibitors in the coolant at the correct strength. If the coolant is left in the sytem too long the corrosion inhibitors become depleted (even though the coolant looks nice and green and "checks" good for temperature protection) and the engine and cooling system can corrode internally. This leads to failed head gaskets as the steel core of the laminated head gaskets will start to corrode from the edges at the coolant jackets and eventually just rot away from the inside out. Purely an issue of lack of maintenance by the previous owners.

    The Northstar is very easy to repair in this case as even stripped head bolt holes can be easily repaired with the correct Timesert thread repair inserts. It just takes a knowlegable mechanic with the proper tools and instruction. A factory shop manual is absolutely mandatory doing repairs to the engine as it does require special assembly and bolt tensioning techniques.
    Well said Anthony and I totally agree....unfortunatly now is the time people with the 93-95 engines will pay the price for lack of maintenace on these cars.

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    Re: So how many people have had overheating/bad head gasket problems?

    Quote Originally Posted by Realtor1
    Well said Anthony and I totally agree....unfortunatly now is the time people with the 93-95 engines will pay the price for lack of maintenace on these cars.
    Don't get me wrong, I agree with the maintanence issue. That's holds true with anything. But you can't answer every problem with that.

    All I'm saying is that was not the cause of my failure. The motor was replaced 03/97 (new coolant) and was down again for a coolant hose again in 99. That was the first owner. The next owner had serviced the cooloing system at least once. And that was one of the first things I did as well. the motor now has 73k on it. The right now the motor is down and there is no corrosion in this system, with the possible exception of the block threads for the head bolts.

    A deteriorated head gasket, no matter the cause, should not cause the head bolts to pull. In my motor the head bolt issue caused the head gasket failure, not the other way around. The head gasket it self looks as good as the new one. It's tough to prove without some extenstive tests (that I don't have the eqipment to do), but I beleive the block threads were damaged before they were removed (and again, they should still be removable). I would assume from the thermocyling, with a possible contributing factor being stress at installation. Both issues being a design considerations.

    I am not a professional engineer or even mechanic, but I've had enough engines apart to know a design weakness is when I see it. I've also owned many cars, as well as those of friends and family, and have never seen such a thing. IMHO this is not a normal failure. How many head bolt kits do you see from Time-Sert for any other engine?

    Thats my story and I'm stikin' to it.

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    Re: So how many people have had overheating/bad head gasket problems?

    No opinion here, just what I ride and what i maintain.

    95 sls 141k puchased with 122k. Coolant was a clear type that checked for temp ratings. I carefully cleaned and degreased the radiator fins with a good shop spray cleaner and mild hose pressure in both directions. I burn 93 Amoco exclusively, with 1 oz Redline S1-1 fuel conditioner per fill up.

    Oil is changed per 2500 miles with AC FIlter...(Valvoline Max life 10-30.)

    Battery is DieHard Gold..100 month and fluid kept up. .. Best I could get type.
    I change paper filter when I change oil, as I do with all vehicles for best performance.

    Added 4oz of Bars Leak once.

    Just did three short trips on Interstes here in SC and Georgia. 80 in traffic...201 Degrees max. (90 -95 into the wind goin to Macon 205)

    100+ in short bursts alone and comin home 203.

    It may blow tomorrow, but so far this is a fine ride.

    I spend more time on cold start warm up, as it is an all alloy engine with a different expansion need than Castion.


    Hope this helps. ljk :coolgleam

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    Re: So how many people have had overheating/bad head gasket problems?

    Quote Originally Posted by ljklaiber
    No opinion here, just what I ride and what i maintain.

    95 sls 141k puchased with 122k. Coolant was a clear type that checked for temp ratings. I carefully cleaned and degreased the radiator fins with a good shop spray cleaner and mild hose pressure in both directions. I burn 93 Amoco exclusively, with 1 oz Redline S1-1 fuel conditioner per fill up.

    Oil is changed per 2500 miles with AC FIlter...(Valvoline Max life 10-30.)

    Battery is DieHard Gold..100 month and fluid kept up. .. Best I could get type.
    I change paper filter when I change oil, as I do with all vehicles for best performance.

    Added 4oz of Bars Leak once.

    Just did three short trips on Interstes here in SC and Georgia. 80 in traffic...201 Degrees max. (90 -95 into the wind goin to Macon 205)

    100+ in short bursts alone and comin home 203.

    It may blow tomorrow, but so far this is a fine ride.

    I spend more time on cold start warm up, as it is an all alloy engine with a different expansion need than Castion.


    Hope this helps. ljk :coolgleam
    Paper filter above was meant to say AIR Filter, Castion means Cast Iron. Sorry bout my typing...lol

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    Anthony Cipriano is offline Cadillac Owners Fanatic
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    Re: So how many people have had overheating/bad head gasket problems?

    Quote Originally Posted by Lawrence
    How many head bolt kits do you see from Time-Sert for any other engine?
    Most every aluminum engine has some sort of thread repair process. Stripping threads in aluminum parts is pretty common in service as the threads are obviously not a strong as cast iron and they can be easily damaged through galling and debris and cross threading and such.

    The timesert kit was developed as a normal development process for designing the necessary service tools before the engine ever went into production. It was not something that was done in response to head bolt problems. It was done as normal due care to provide the necessary tools to repair the engine in the field.

    Stripped threads are not something that's necessarily expected or anticipated when designing an aluminum engine but understanding aluminum it's obvious that threads can be damaged and that repairs will be necessary. In aluminum and with highly loaded joints like the head bolts there are a lot of thread repairs that wont work (like heli-coils in specific) so the service kit was developed and validated with time to make positively sure the correct tools and materials were in the field for successful service.

    It's hard to say without seeing the parts what happened to the head bolts in your engine. It is pretty rare for "all" the head bolts to just pull out like described. The failures of head bolts usually happen at assembly when the threads are not cleaned or the tech cleans the threads with a cutting tap (quickest way to ruin the threads) or something like that. Occasionally a thread will fail when being tensioned due to some porosity in the casting in that area weakening the threads but for them to just "pull out" is something that's hard to understand.

    There was a great deal of sealing and fastening work done on the head bolt joint on the Northstar. The fact that it's under a lot of load and stress and that aluminum expands more than steel was not "missed" by the engineers involved.

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    Anthony Cipriano is offline Cadillac Owners Fanatic
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    Re: So how many people have had overheating/bad head gasket problems?

    Quote Originally Posted by becker_jr
    On the bolt problem, that Lawrence is writing about.
    I have heard from the workshop that the bolts today are of a kind, which are tightened not with specific torque, but instead a specific angle. These bolts are called tension-bolts. You get the intended force to hold down the top through the head gasket to the engine block through, as it were, a spring, although with restricted elasticity. Sometimes these bolts snap, usually were the thread is. In order to remove these, GM is said to have developed a special tool enabling the removal of that part without having to take off the top. That is supposing that the head gasket is not leaking.
    It seems that broken tension bolts is not that uncommon as witnessed here .
    A search for “tension bolt” using Google returns 1690 hits.

    My car did not have that problem though.
    Good observation. But there's nothing specifically different about the bolts in the way they work. "Tension bolts"? All bolts are tension bolts. That's how bolts work! There's nothing unique in the Northstar head bolts in this area.

    Every bolt is considered a "spring" as described. The bolt is installed and tightened. As the bolt is tightened it's stretched to tension it - to impart a spring load or "clamp load" on the joint. A sealing and fastening engineer will design the joint and the gasket to require a certain clamp load to seal, and, based on the load of the parts in operation, the clamp load must have exceded that working stress to hold the joint together. The bolt is simply a long spring. If you put a bolt in a machine and stretch it you will see a spring rate for that bolt. Bolts are generally very stiff so they don't stretch much - and as they stretch that little bit the force required to stretch them goes up astromonically. But it's at a rate none-the-less. So, if the load required to seal the joint is a certain amount and the spring rate of the bolt is known then it can quickly be determined how far the bolt will have to be stretched to get that load. Once again, nothing unusual here, all bolts work this way.

    The thing that's unique in a way about the bolts in the Northstar is the means used to tension or stretch them. Torqueing a bolt is a misnomer in a way because it's an indirect measurement of the amount of stretch in the bolt. It would be much more desireable and accurate to measure the stretch of the bolt directly. This is often done with critical fasteners like rod bolts where the bolt is open at both ends. ARP commonly gives the specs to tension the high performanced rod bolts in terms of the amount of stretch to be measured with a micrometer. Just turn the bolt until it stretches a certain amount. With head bolts this can't be done as the hole is blind. To get the similar accuracy the spec is given as a torque and angle - such as 80 nm plus 180 degrees. The torque is speced to just get the joint to zero clearance - pull all the slack out of it. And the angle is based on the thread pitch. Turn the bolt that many degrees and the tread pitch will stretch it that much ie. if the bolt has a 1mm per turn pitch and you want to stretch it 0.5 mm to get the necessary load then the "angle" would be 180 degrees. Half of a turn or half of the 1mm thread pitch. Simple as that. All bolts can be tensioned this way - not just the Northstar bolts.

    Torqueing a bolt is a notoriously inaccurate way to tension it. The "torque" being applied is used up in friction in the threads, friction under the head of the bolt and to stretch the bolt. If the friction changes even a little it affects the amount of torque used to stretch the bolt (and tension it) dramatically. So, the torque-angle method is used to minimize this. The "torque" given is very low. Just enough to zero the joint and not create a lot of friction in the threads or under the head. Then the "angle" spec actually stretches the bolt accurately based on the geometry of the threads. This also helps to eliminate inaccuracies from oil and grease on the threads and such as the "angle" ignores this. Plus, if a bolt bottoms out in a hole then it will be self policing as it'll be impossible to turn the bolt to the prescribed angle - as it'll stop when it bottoms. If torque alone is used, a bottomed bolt will check "tight" even though it is not clamping the joint.

    There are some bolts used in engines called "torque to yield" where the bolt is actually designed to deform as it's tightened. A torque to yield bolt can only be used once as every time it's used it gets longer and longer and eventually will snap in two. The Northstar head bolts are not torque to yield fasteners. They're specified for one use only as they are highly loaded and require the proper anti-lock coatings applied to them. The blue thread coating and the red coating on the washer act as installation high pressure lubricants and then thread locking agents so the head bolts don't loosen. Aluminum engines like to loosen the head bolts if they aren't locked in place. Ask Honda about that...

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    Anthony Cipriano is offline Cadillac Owners Fanatic
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    Re: So how many people have had overheating/bad head gasket problems?

    Quote Originally Posted by ljklaiber

    Coolant was a clear type that checked for temp ratings.


    Added 4oz of Bars Leak once.



    I spend more time on cold start warm up, as it is an all alloy engine with a different expansion need than Castion.

    :coolgleam
    A couple of observtions. The reason that the coolant must be drained and replaced is that it has corrosion inhibitors in it that deplete over time. That can't be measured. Even though the coolant might check fine for temperature protection it must be drained and replaced occasionally. The coolant is mostly ethylene-glycol - that's what provides the freezing and boiling protection. The EG is usually fine and could last forever. The corrosion ihibitors, however, don't last forever, particularily with the green conventional silicated coolant.

    The green stuff used prior to 1996 must be replaced every 2-3 years/24-32,000 miles. The orange DexCool (that your car should have come with) will last 5 years /100,000 miles although replacing it more often doesn't hurt. There is no approved coolant that's "clear". I would drain the system as completely as possible and refill with fresh 50/50 DexCool/distilled water for the most protection of the cooling system.

    The system is factory filled with the coolant supplement/sealer and that should be used at each drain/refill to avoid nuisance leaks. Aluminum castings will exhibit a certain level of porosity over time so the sealer is used to prevent leaks. Personally, I recommend 6 of the GM coolant supplement pellets or two tubes of the BarsLeaks "golden seal" to seal the system in a Northstar. The sealer must be installed in one of the radiator hoses and not the surge tank. There's little active flow through the surge tank so the sealer cannot disperse through the system.

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