Head Bolts, fixed by what year?
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Northstar Engines and System Technical Discussion Discussion, Head Bolts, fixed by what year? in Cadillac Engine Technical Discussion; What year did Cadillac address the problem with head bolts on the Seville?...
  1. #1
    Jesda's Avatar
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    Head Bolts, fixed by what year?

    What year did Cadillac address the problem with head bolts on the Seville?

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    Re: Head Bolts, fixed by what year?

    Im pretty sure it was in 00, I know the new ones have been attended to.....

    Ill move this to the northstar section...

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    Re: Head Bolts, fixed by what year?

    There is no specific "fix"... Over the years there have been a variety of directionally correct changes to the head bolts to increase the integrity of the fastene engagement into the block threads. The head bolt threads have been increased slightly and the block thread height was also raised to increase thread engagement slightly. The metalurgy of the block in the area of the head bolts as been under development to reduce any porosity and improve thread strength. The RWD Northstars and the 2004 and later FWD engines have a redesigned head bolt with a 2.0 mm pitch (coarser thread) for better engagement.

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    Re: Head Bolts, fixed by what year?

    Is there a particular year when the problem is worst? Say theres this asian guy named "Jesda" who is thinking about buying a Seville... what years onward seem to be the least problematic regarding this issue? 1998+?

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    Re: Head Bolts, fixed by what year?

    It seems that the older ones, 97 and older, were more prone to it... But, a lot the higher mileage 98+ have to be highway mileages...

    Maybe Jesda is asking, "are the 98+ sts northstar different than the 93-97"

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    Re: Head Bolts, fixed by what year?

    You can bet that buyers of 1998 and later model years will start showing up here moaning about head gaskets and a very large percentage of those engines will still contain the factory fill of Dex-Cool.

    If you are buying a used Northstar-powered ride, try to document that the previous owner(s) observed the 100,000 mile / 5 year coolant change recommendation for Dex-Cool, or walk away from it

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    Re: Head Bolts, fixed by what year?

    As Bbob said, there is no "fix". All Northstar's have a degree of weakness in that department. Cadillac has done several things over the years with varying degrees of success but bottom line, the problem still persists. IMO, the new RWD Northstar S/C has the best shot of keeping it's coolant in the water jacket where it belongs but with the increased combustion pressures brought on by the forced induction only time will tell. Now if they did the bore reduction on a naturally-aspirated engine, THAT might be the ticket for longevity. Who knows?

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    Re: Head Bolts, fixed by what year?

    It seems as though, in addition to addressing the physical material problems of block casting porosity, thread engagement and thread type, the GM powertrain engineers would design in a more capable cooling system that reduces the effects of thermal cycling by not allowing the huge swings in engine temperatures now considered normal. Calling 245ºF "normal" is really stretching things. Whether this means cooling fans with higher speed capability, more efficient cooling fan blade design, a larger radiator, a radiator with more rows of cores or a combination of all of these, this certainly wouldn't hurt and would be relatively inexpensive to implement. (as compared to the cost of lost customers and continued downward spiral of market share) A coworker has an '01 Northstar with under 100,000 miles with headgasket/headbolt issues, so the problem didn't completely go away in '00. BTW, the owner now refers to his Northstar as "The Steam Engine" (LOL) and keeps two gallons of premixed Dexcool in the trunk and adds coolant more often than he fills up with gasoline.

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    Re: Head Bolts, fixed by what year?

    Quote Originally Posted by blb
    It seems as though, in addition to addressing the physical material problems of block casting porosity, thread engagement and thread type, the GM powertrain engineers would design in a more capable cooling system that reduces the effects of thermal cycling by not allowing the huge swings in engine temperatures now considered normal. Calling 245ºF "normal" is really stretching things. Whether this means cooling fans with higher speed capability, more efficient cooling fan blade design, a larger radiator, a radiator with more rows of cores or a combination of all of these, this certainly wouldn't hurt and would be relatively inexpensive to implement. (as compared to the cost of lost customers and continued downward spiral of market share) A coworker has an '01 Northstar with under 100,000 miles with headgasket/headbolt issues, so the problem didn't completely go away in '00. BTW, the owner now refers to his Northstar as "The Steam Engine" (LOL) and keeps two gallons of premixed Dexcool in the trunk and adds coolant more often than he fills up with gasoline.

    There is plenty of engine cooling for the package. That has nothing to do with it. 245 is not that hot, really. It may seem hot to you but it is well within the capability of the cooling system to control the engine temperature and is well below the boiling point of the coolant and cooling system. The physical properties of the aluminum block and head are not affected within that temperature range. If the engine has head gasket problems then it isn't because of the cooling capacity.

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    Re: Head Bolts, fixed by what year?

    as far as cooling engine temps down i dont think that will ever happen, the higher temps produce lower emissions and unless you live out where i do and dont have to be tested you can run a cooler thermostat and all but as far as GM cooling them down i dont see that every happening

    i wonder if a cooler thermostat is made for the nortstar, like a 180 degree unit that what i run in my tpi small block firebird? hmmmmm

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    Re: Head Bolts, fixed by what year?

    Quote Originally Posted by bbob
    There is plenty of engine cooling for the package. That has nothing to do with it. 245 is not that hot, really. It may seem hot to you but it is well within the capability of the cooling system to control the engine temperature and is well below the boiling point of the coolant and cooling system. The physical properties of the aluminum block and head are not affected within that temperature range. If the engine has head gasket problems then it isn't because of the cooling capacity.
    245 degrees isn't too bad, that's true. I had a '78 Pontiac Grand Prix with a 301 V8 and it would "normally" run around 215 or so. That "seemed" high because most other engines at the time were easily running under 200 degrees. I think it's just a matter of what people are "used" to, not what's actually good or bad for the engine. But then again, it IS getting close to the max. for the coolant as I recall.

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    Re: Head Bolts, fixed by what year?

    Quote Originally Posted by Katshot

    it IS getting close to the max. for the coolant as I recall.

    If the coolant is at 50/50 concentration and the system pressure cap is working correctly at 15 PSI the system will not boil until 265 degrees F. 245 is 20 degrees away from boiling...as good as a mile in engine cooling work....LOL

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    Re: Head Bolts, fixed by what year?

    Quote Originally Posted by bbob
    If the coolant is at 50/50 concentration and the system pressure cap is working correctly at 15 PSI the system will not boil until 265 degrees F. 245 is 20 degrees away from boiling...as good as a mile in engine cooling work....LOL
    If you say so. I'm just glad I don't have one of those aluminum time-bombs under MY hood!

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    Re: Head Bolts, fixed by what year?

    The theory:
    In rough numbers, Thermodynamic tables and formulas will show you that for each 1 psi of pressure, you will raise the boiling point of water about 3 degrees F. Therefore, with a 15 psi cap, your boiling point will be somewhere in the neighborhood of 257 degrees F. A 16 psi cap will raise the boiling point to about 260 degrees F. Add to this the fact that you aren't running straight water, the boiling point is even higher since the antifreeze mixture has a higher boiling point than straight water. This assumes you have a tight cooling system, a good cap, perfect radiator, good headgaskets, no leaks etc. Any loss of pressure will lower the boiling point accordingly. All this is well and good on a new vehicle with all new hoses, radiator cap, good water pump and radiator, etc.

    Reality:
    Fast forward 10 years where you have a vehicle not capable of holding the required pressure for a variety of reasons, and you've got trouble. I realize there is no excuse for not maintaining a vehicle, but this is the way it is and at these high coolant temperatures, there is more of a chance of a boilover when all the systems are not like new or not properly maintained. In other words, there is less of a factor of safety for boilover at these higher engine temperatures.

    As far as the higher engine temperatures being "required" to pass emissions testing....not necessarily so. Obviously, the higher engine temps are better from an emissions testing standpoint. But remember, anyone who has had a Northstar for a number of years and has kept an eye on the engine temp readout will realize that in a typical Northern US winter, (ambient temps 10 to 30 degrees F) you can idle all day or run WOT all day and you'll never see a 245 degree F engine temp. Fast forward to summer and sit in a traffic jam in 110 degree heat for a few hours then run a few WOT's up steep hills and you very well may see 245 degrees F. Does this mean the car won't pass emission testing in the winter but will in the summer? Obvoiusly the answer is NO. Therefore, my point is why let the engine temperature fluctuate so much when, with computerized engine controls and cooling fan controlls, it would be relatively easy to reduce the variation in temperature if the cooling system was capable.

    Also, the more thermal cycles, and the greater the spread of temperatures during each cycle, has to be a factor of some significance in headgasket longevity.

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    Re: Head Bolts, fixed by what year?

    The 245deg. is childs play for liquid cooled engines. Liquid cooled aircraft engines routinely operated at 350 deg. and above. Of course there were higher pressures and concentrations of ethynene glycol. It's hard to find a car made in the last 20 years that doesn't have a 13-15 lb. pressure cap and runs at similar temperatures. The difference is that the gauge on the panel just shows hot and cold so you don't know what the actual temperature is. With the Caddy you can call it up digitally. Why not just drive the car and be happy like everyone else is. Ignorance is bliss.

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