: Head Bolts, fixed by what year?



Jesda
01-15-05, 11:23 AM
What year did Cadillac address the problem with head bolts on the Seville?

elwesso
01-15-05, 09:08 PM
Im pretty sure it was in 00, I know the new ones have been attended to.....

Ill move this to the northstar section...

BeelzeBob
01-16-05, 02:23 AM
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.

Jesda
01-16-05, 09:16 AM
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+?

elwesso
01-16-05, 11:46 AM
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"

JimD
01-16-05, 01:11 PM
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

Katshot
01-17-05, 08:15 AM
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?

blb
01-17-05, 12:46 PM
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 245F "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.

BeelzeBob
01-18-05, 01:35 PM
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 245F "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.

cart69
01-18-05, 01:43 PM
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

Katshot
01-18-05, 03:06 PM
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.

BeelzeBob
01-18-05, 10:53 PM
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

Katshot
01-19-05, 08:23 AM
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! ;)

blb
01-19-05, 07:54 PM
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.

dkozloski
01-19-05, 10:27 PM
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.

32V_DOHC
01-19-05, 11:19 PM
The bolts themselves I see as a red herring. They are rarely a problem until they need to be removed. Same thing for coolant temp. The engine can easily goes from 0 degrees to 225. Do you really think that last 20 degrees is going to radically change the joint if the coolant doesn't boil?

Most of the failure seem to surrond the steel core corroding out of the headgasket. The root of this is almost always poor cooling system maintainance. Whether it is failure to change the coolant or letting it get too low or adding corrosion prone ion filled water the problem could have been avoided by proper maintainance.

That being said I am kind of disappointed in Cadillacs response to this problem. Don't get me wrong I love the cars they build but Cadillac should know poor cooling system maintainance is rampant. Failures are bad for business and the brand name. One would think a coolant life monitor and change reminder would be high on engineerings wish list. Protecting the metals from corrosion protection depletion would have a dramatic increase on long term reliability. I also wonder about headgasket design. If the gasket core rots out because it is in contact with depleted coolant then why not change the design to insulate it from that contact. Coating the gasket coolant passages should add little cost and would chase the problem somewhere else. I would think that designing the radiator to fail by corrosion before the engine would be a wise move. Just my 2 cents.

John

BeelzeBob
01-20-05, 12:02 AM
[QUOTE=blb]

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.

QUOTE]


I don't disagree with your other comments in theory....but the reality is that the head gaskets, all the engine components, the cooling system, etc..is thermally tested under much harsher conditions than in found in the real world before the design is released for production. The gasket joints in the engine are subjected to a very severe "deep thermal cycle" test including cyling the running engine to a temperature cycle from -40 coolant to 265 degree coolant thousands of times in a forced cycle on a dyno to rapidly thermal cycle the joints to make positively sure that they will live under those conditions. The idea of thermally induced stress on the gaskets and other engine parts is not lost on the engineers that designed the engine....it is designed for that and will operate under the design conditions fine.

The concept of putting a cooling system in the car that would ALWAYS keep the coolant dead on 210 or something is not a bad idea....it is just extremely impractical. It would take a huge radiator, large cooling fans, bigger alternator to power them, etc....to keep the temp constant under all conditions. That is a lot of unnecessary mass for all the cars to haul around for just the few that are occasionally subjected to extreme conditions. Just not practical...and totally unnecessary.

The engine thermostat keeps the engine temperature stable on the low end. Most of the cars most of the time operate very closely between the stat temp and 225F where the cooling fans activate. Hotter conditions and higher loads and grades will drive the temp up to 245 or higher on occasion. That is perfectly acceptable and does not damage the engine or degrade it's life. There is a lot of work arriving at the design and sizing of the cooling system to be able to adequately cool the engine for what it is required to do vs. the extra cost, mass, complexity induced by "overcooling" it. Should all cars cost more because cars for Phoenix needed a larger cooling sytem...no. They all get the same cooling because they may all drive thru Phoenix one day...so they are all designed to handle that eventuallity.

Granted, the cooling system is designed, capacity wise, to operate in it's designed condition. Yes, maintenance is important. That is why things like long life thermostats, DexCool coolant, silicone hoses, etc...were all developed and put on cars. It isn't that hard to make sure the cap is clean and sealing and that the hoses are not leaking. The coolant does not loose it's boil/freeze protection (the ethylene glycol does not wear out...just the corrosion inhibitors wear out...so DexCool was invented) I think that the performance of the current cars is becoming their own worst enemy in a way. Little or nothing is done to the cooling systems on the majority of cars on this forum with well over 100K on them.....and you expect them to cool as perfectly as they did when they left the factory. Imagine a simple radiator hose lasting 10 years and 100K on a 1960's era car....LOL LOL LOL And people talk about the "good ole days".... LOL LOL

cadillactech
01-22-05, 08:59 AM
The 1997 models were the worst about pulling the threads out of the blocks on the head bolts. Our shop has done mostly '96, '97, '98's. Maybe only one '99. I think that for whatever reason, they got things straightened out in 99.