High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps
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Northstar Engines and System Technical Discussion Discussion, High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps in Cadillac Engine Technical Discussion; High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps...Seems too frequent not to be an eyebrow-raiser. Let ...
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    BlueMoon is offline Cadillac Owners Member
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    High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps

    High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps...Seems too frequent not to be an eyebrow-raiser.

    Let me start out by saying that I'm the proud owner now of a 96 ETC with the N*. I Love the car, it's looks, it's power and am impressed by the overall engineering of everything on the vehicle Except for one thing... the cooling system. I've noticed firsthand and reading on here thru countless posts that it's "typical" for temps during normal driving to cycle between around 190 to 230(some have even reported up to 250). I may be an "old school" wrench but even as much as technology has changed over the past few years, I am Not surprised that blown head gaskets and high oil consumption are mentioned so frequently.

    Over the years it has become a well known fact that aluminum engines are more heat critical. Me, I like to keep my vehicles nice and in excellent working condition(and for a long time). This is why all of this is so bothersome. In the twenty-some odd years of GMs I've owned they've all had stable running engine temps and... I've religiously changed all my stock 195 thermostats out for 180's. I'm sure I'm gonna spark some heated debates here on that subject(and it is Not the subject I'm aiming to drum up some friendly discussion on) but it has worked VERY well for me over the years. I myself wrench and my past experience with this keeps gaskets from getting brittle and losing their seal, oil lubrication qualities high and better power and fuel economy from less detonation. The big thing to me is the longevity. In the many vehicles I've owned I've Never had Any internal mechanical failure, leaks or even oil consumption problems Ever. I've Never had any emissions passing problems either(Except for 2 of my 170,000 + mile vehicles needed a new cat as the pellet type just plain wore out.) I keep my vehicles for a long time and I also like to drive them "hard" from time to time too. So call it just good luck if you want.

    Getting back to the subject of my post...
    230+ running temp is too high for my liking(that's just my personal opinion). Sure maybe gasket and oil technology has changed over the last few years but that's just plain cooking hot in my book. Rings gummed up with "coked" oil... I'm not surprised. Early & excessive oil consumption...I'm also not surprised. Failing gaskets...you don't say. Just think how much even more heat your engine sees with heat soak(after turning the car off). Also not to mention you'd Never make it home having to put just plain old water in your cooling system from way out in the boondocks after say a hose failure. But OK. Lets just say "normal" it is per GM. What my bother is mostly about is in the stop and go temp fluctuations of this car. Think of it this way... if the aluminum of the engine is constantly changing from 190 to 230 as you idle then drive: 230 - 190 = 40 degrees of CONTINUAL temp fluctuation. If you don't think that's a big deal drop a 30 degree ice cube into a 70 degree glass of soda....but Keep doing it. Sure that's kind of an extreme comparison but that much of a continuous "Swing" CAN'T be good for the expansion of an aluminum engine held together with steel bolts. Bars leak or not, it just seems like a problem waiting to happen from a machinists and a mechanics standpoint. All of my past vehicles had stable operating temps, why not this one I've been asking myself...

    So in I jump under my hood... replacing the thermostat(from the dealer), checking the water pump, belt and tensioner, pulling the radiator and inspecting the tanks & tubes, changing the hoses and ultimately the coolant(after a good flush). Everything is A+. Even the coolant lines, restrictors and the heater core all flow well. Still I get temps all over the place(190-229). That's even in the cold Chicago weather here. My fans are functioning(kick on LOW at 225), but still even with the vehicle moving in very cold airflow it's still all over the place. Definitely not stable.

    Can someone tell me... am I seeing things or is the thermostat mounted on the coolant RETURN side INTO the block?(cooled water coming FROM the radiator flows thru the thermostat???) Please tell me that's NOT so!

    (Unless there's something wrong with my eyesight it looks like the RETURN line from the heater core is the only thing that heats the thermostat up to open. And that would be mixed with the cooled water coming from the radiator too!)

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    BeelzeBob's Avatar
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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps

    I understand your thinking and line of thought....but....it really isn't correct.

    Coolant temps in the range of 230 are perfectly normal and desireable.

    As long as the engine is "wet" and full of coolant that is circulating it will not be damaged and can run as hot as 270 degrees or hotter for EXTENDED periods of time without hurting a thing.

    A system that has a 50/50 mix of ethylene-glycol coolant/distilled water and is pressurized to 15 PSI (normal OEM cap) will not boil until 265 degrees.

    There is little to no correlation to ring belt deposits and coolant operating temperature.

    There are millions of Northstar engines on the road that operate perfectly fine at those operating temperatures. You read about a few problems on this and other forums....but...forums are like that. Everyone with a problem looks up a forum for help/information/commiseration/venting...but few look up a forum to brag about their Northstar with 200K miles on it....

    I have seen MANY endurance and durability engines that ran 100K miles of heavy duty use in the Phoenix (GM Desert Proving Grounds) area and off property in the hills and grades of the desert south west. Those engines LIVED at high coolant temps all their lives and they look fine inside. Better, in fact, than engines running "cool" in cold climates.

    I have personally run many high speed endurance engines on dyno test (full power, 6000 RPM, 300 hours) at elevated coolant levels and the engines just do not care if the coolant is at 210 or 250 or 180...... They hotter they run the better they look, actually.

    Based on your observations of the coolant temp in your 96 ETC I would ask...is this your first experience with a FWD car with electric cooling fans..?? I suspect from what you say it may be as the temperature excursions you observe are more a function of electric cooling fans than anything else. Electric fan cooled cars typically have fairly regular coolant temp excursions due to the lack of air flow thru the radiator when the car is not moving. Older cars with longitudinal engines (typical RWD) had engine mounted fans that always pulled some air thru the radiator. Cars with electric fans have NO airflow at low speeds and idle so the coolant temp naturally creeps up...until the fans turn on...then the temps go back down.

    You will notice this much more in the winter and cool weather than in the summer. In the summer, when the AC is on the fans will run most all the time due to the requirement for constant airflow over the condensor for the AC. The AC system has almost no thermal inertia unlike the engine cooling system therefore it needs the constant air flow. When the fans are running due to AC requirements they provide radiator airflow by default so the coolant will stabilize more at the stat temp. In ambients below about 40 degrees the AC compressor is disabled (or when you drive on ECON or OFF) so the fans only run when the coolant gets to 225F. That is perfectly fine and is as designed. Seems odd at first to notice more coolant temp swings at colder ambients but that is the nature of the beast with electric cooling fans.

    Putting a lower temperature stat in the engine is counterproductive to the engine control system as many coolant thresholds in the calibration are based on the operating temp of a 195 stat (which usually controls around 205-210 in the engine) as designed AND the stat control temp is closer to the fan turnon temp of 225 F Coolant so as to minimize the amount of temperture cycling of the engine. Putting a colder stat in increases the amount of cycling that you are observing as the engine will cool down to the lower stat temp when moving/fans on and then heat back up to the 225 fan on temp when idling/city traffic.

    It is desireable to get the coolant above 212 F so as to heat the oil above 212 in city driving quickly so as to boil out moisture and raw fuel that gets in the oil on cold starts. Running colder thermostats is detrimental to engine life from this aspect, particularily in colder climates and in short trip/urban driving that doesn't heat the oil up otherwise.

    The Northstar cooling system is a very sophisticated, high flow system that is designed for a high output, high RPM, all aluminum engine...not a system that was adapted from an older, slower turning, cast iron, low output engine. The water pump on your 96 will pump around 105 gallons per minute at 6500 RPM (that is TWO 55 gallon drums in 60 seconds....think about it) while requiring a minimum of power to do it. It is a very efficient water pump impeller design that is designed to turn high RPM and move a lot of water.

    The main consideration of an all aluminum engine is NOT the absolute coolant temps observed but maintaining thermal stability throughout the engine. Keeping the hot spots cool and the cool spots hot eliminates thermal fatigue of gaskets and seals and allows the engine to "grow" and "shrink" with coolant temp changes as a single entity...not dissimilar parts that stress the fasteners and gaskets. This is accomplished by having VERY HIGH coolant flow rates thru the block and heads constantly so as to maintain an even temperature gradient across the engine regardless of the observed coolant temp.

    Keeping in mind that the water pump can pump about 105 GPM at 6500.....only about 45 GPM is directed to the radiator. That is sufficient for the heat rejection required and is the maximum that is allowable for the long term life of the radiator....erosion of the tubes, tanks, and end-tank oil coolers would result with more flow. So....where does the other 60 GPM go....???....it is recirculate back thru the block and heads in a re-circulation loop....part of which is the heater core circuit which accounts for about 7 GPM of flow at maximum engine RPM. The main part of the recirculation circuit is the cast passages inside the water crossover casting that the water pump resides in. When you remove the stat you can see one of the coolant bypass passages at the end of the thermostat mounting port...the large hole that the spring loaded paddle covers.

    The inlet thermostat design is used to minimize the efficiency of the water pump and to limit thermostat induced temperature cycling in colder weather. The stat has many functions. The spring loaded paddle at the end closes off the bypass port (the bypass that bypasses that 60 GPM back thru the heads and block) until sufficient coolant pressure blows it off and establishes flow. Under normal conditions the temperature sensing element is bathed in the bypass flow consisting of the direct bypass port, the heater core circute and "cold" water that is being admitted by the thermostat. This lets the stat see a true operating temp of the engine as opposed to a more conventional exit side stat that only sees coolant temp when it opens and coolant is flowing past. Nothing wrong with your eyesight....you just have to dig into the engine and the passages in the castings to understand the cooling flow path...or get a service manual and it is spelled out very clearly in a nice diagram for you.

    The water pump in the Northstar is prone to "vapor lock" if it injests any air bubbles so the water pump cavity is continuously bled or air or bubbles thru the vapor vent line that is the 3/8 hose leading from beside the upper radiator hose to the pressurized surge tank.

    The system uses a pressurized surge tank as the high point of the system so as to de-aireate the coolant in a quiet, low flow area, allow for expansion and contraction of the coolant, provide a means of real time low coolant level warning BEFORE it impacts cooling capacity, and, primarily, provide a source of clear, pressurized coolant directly to the water pump inlet port to prevent the pump from cavitating in high demand situations. The heater core circuit exits the water crossover casting after the coolant traverses the block/heads and returns thru the circuit from the pressurized surge tank to complete the circuit and supply a constant feed of fully pressurized coolant to the water pump inlet where the negative pressure would be the greatest and cause cavitation.


    Before you start redesigning or re-engineering the cooling sytsem on the Northstar engine you really need to understand how it works, why it is designed the way it is and what the impact of your design changes are. There are thousands of hours of development time in the cooling system of the Northstar and the vehicles it is installed in. It was not taken lightly, trust me. Basically, it serves as a very good example of a high performance cooling system for a high out put engine. There is nothing that was compromised on the cooling system design and the design features pioneered on that system in 1993 have been incorporated in other high performance cooling systems throughout the automotive industry....i.e...pressurized surge tanks, vapor vent lines and continuous air bleed systems, inlet side thermostats, high bypass ratio cooling porting, very high flow water pumps, etc....


    BAsically, every thing you did is perfect to make sure the system is in top operating condition. The one thing you did not mention is the addition of the GM Coolant Supplement pellets to the system to guard against any incidental leaks from porosity in one of the aluminum castings or a gasket imperfection. It is designated as a required item in the cooling system. Search the archives using "coolant supplement" as a topic and read my posts for more info on this as much has already been posted.

    You are, however, trying to fix something that is NOT broke. Put the OEM stat back in as that is what is best for the car and engine. It will actually reduce the level of coolant temp swings you are seeing in cold weather, will warm the engine to the temperatures the clearances were set up for, will match the PCM calibration set points for coolant temperature and it will improve the oil life and oil quality particularily in cold weather. Keep the system full of 50/50 Texaco DexCool/distilled water and install the 6 coolant supplement pellets into one of the radiator hoses....not the surge tank.


    YOu make a good point about the thermal distress that can be caused by continual coolant temp changes...to a degree this is a concern and something that the engine developement engineers take into account. Thermal fatigue of gaskets and such is what it is called. The problem or concern is mitigated, however, by the very high flow rate of coolant thru the engine, the high rate of coolant bypass that is already heated by the engine and is simply bypassed to stabilize the internal temps and the higher operating range of the OEM stat that more closely matches the coolant temp that the electric fans engage at. Lowering that stat temp with a "180" stat makes the situation WORSE not better. The thermal fatigue issue of the gaskets and engine internally is also mitigated by the fact that the WHOLE engine structure changes at once due to the high coolant flow rates. If the parts all grow and move and shrink TOGETHER then there is minimal fatigue of the gaskets and such. This is one reason the engine lasts as well as it does in fact. Most all of the head gasket problems and such mentioned on this forum are on engines that have well over 100K on them...unheard of 20 years ago. Furthermore, when dissassembled for repair, the engine look like new inside with nothing other than head gaskets and (occasionally) a head bolt thread repair. If the cooling system was not working correctly on an all aluminum engine that turns 6500 regularily and makes over 1 HP per cubic inch it would fail MUCH sooner.

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    blunted is offline Cadillac Owners Enthusiast
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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable T

    That was another very good thorough explanation.. someone add it to Bbob's memoirs! Make's you happy to own a caddy , and shows the true strong points of these cars and their design which people forget to acknowledge in the middle of them only stressing it's shortcomings. I know one thing, this is the only car I've owned and been in that has been complimented so much, even once by a guy driving a brand new S600 while smoking his imported cigar.. he was very impressed how the caddy sounded with its mufflers and the way it moved. :coolgleam Gotta love dem caddys!

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    BlueMoon is offline Cadillac Owners Member
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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps

    I have to disagree with you on a few things.
    Yes, on a dyno hotter is better. That is true in terms of combusion temps and EGT. It
    correlates to thermal efficiency. But I'm speaking in terms of block temperature. I have "some" experience in dyno use in R & D. And higher block/cylinder head temps cause preignition and detonation. That in turn causes lower efficiency and lower power output. Especially in motors that are running higher compression(like todays production cars). Their higher compression "plus's" can't be used. Take a look at when the knock sensors are most commonly cutting back timing... it's when the engine is it's hottest. It's more complicated than that, but that's a simple example. In engine design there's always one good characteristic trait that you can increase while another works against it. But engineers are always searching for that happy balance.

    Engines live "better" at higher temps??? Never from a wear and tear standpoint. Too hot or too cold is Bad.

    Also, no matter how high a flow rate this cooling system has, yes higher flow Will help
    eliminate hot-spots, but you're missing my point in all this...block temp swings and poor regulation(and thermostat location). I'm Not seeing this "thermal stability" you talk about.

    The Northstar is a nice piece of work making more than the "covetted" one horsepower per cubic inch category. But that isn't hard to achieve these days with four valve per cyclinder motors and fuel injection. Even on pump gas. The efficiency of 4 bangers has come to that over the years as they are now making as much power as the V8s of 10 years ago. And they're getting good gas mileage too. But these little everyday 4 cylinders are seeing far more of a duty cycle than the Northstar. The N*s power is rarely even exercised in even aggressive everyday driving. So these motors should Really last. Yes, I know there are millions of them that have not and will not ever have a problem. But we're now getting to the times of warranties lapsing and people buying more of these cars second-hand and working on them themselves. So you're really beginning to see what's going on and what's frequent to happen(as in this wonderful board. My hat's off to all of those sharing their experiences to make life a little easier and "richer" for others). I am not new to engine design and development but I Am new to the Northstar community. It's also seemingly "popular" that if you ask any mechanic what the "weak point" of the N*'s is and what they've commonly seen
    thru the past few years, guess what they're gonna say???? Yes, you guessed it...head gaskets. But, it seems most of them will say it's the Dexcool that caused it. On the flipside there's my point on the temps being all over the place and High. Me, I don't see anything wrong with dexcool. I also don't see anything wrong with the design of the mating surfaces or the gaskets or the bolt threads themselves either so far.

    Your reasoning for design of that high of a block temp doesn't make sense in terms of
    boiling the moisture and deposits out of the oil. Not in that extreme of a measure is what I'm saying. Yes, it is necessary to bring oil temps up to evaporate moisture and some of the other by-products of combustion that get past the rings ...and to attain the desired "fluidity" to create the desired film of oil(to put it in the simplest of terms). But too high of temps will prematurely accelerate the breakdown of the oil and it's desired characteristics. Part of the reason we change our oil is because it becomes contaminated and part is because it's decomposing and losing it's lubrication qualities. And heat accelerates this decomposing process. Not to mention too high of heat Will leave coke-like deposits(sludge) earlier than normal because the oil Really starts to breakdown. The rings and pistons sre one of the hottest parts in an engine. So, Yes and No. You are correct in that the piston and ring temps don't have much to do with coolant temps. They are primarily cooled by the oil. But technically by having the whole "assembly" say 50 degrees hotter just "steps" everything up. I personally don't see this motor not having oil consumption issues starting at even 10K miles without the high oil capacity and oil cooler setup it has. It is Very much needed with this motor in it's "common" temperature range(s).

    Some of the other possible reasons for high block temps that you have not mentioned are increased passenger compartment heating and lower emissions. I could possibly see GM's R & D going for the emissions standpoint, but with today's self-heated O2 sensors and close-knit computer control, the emissions are already very well regulated.

    Yes, I have also had experience in FWD cars and electric fan setups. I'm Very familiar with them. There Is a typical cycling range the fans will keep things in "check" between. But, I've Never come across such a wide range before. I'm trying to keep the subject on the thermostat for the moment. Fans are fans, they do their job depending on when you turn them on and off. I'm talking about the poor engine temp regulation when the car is at 35 MPH + in 30 degree weather(forgetting about the fans). You can wire the fans on HIGH all the time when it's cold out and the block temp is Still all over the place.

    Getting back to my thermostat topic...
    I did some more looking into the placement of the thermostat and it IS as I had suspected. So I am now not surprised with the behavioral characteristics of this car's cooling system. I think I'm even more bothered now than before too. If cooled coolant is flowing thru that thermostat, it's Gonna keep cooling/closing itself making wide swings and cycling. The thermostat in this setup is "fighting" itself.

    Then, I see there being a "runaway" point with this setup. A point where the demand for cooled water by the engine won't be met because the higher amount of cooled water flowing thru the thermostat will cool and close itself... yielding a condition kind of like a reactor going out of control. I can see now why there is a "Limp Mode" initiated by the computer. There HAS TO BE! Let me tell you something... you will NEVER see me "putt-ing" along down the road with no coolant in my motor impressed as all hell that this "baby" is still running and some hot dog engineers are "wise" enough to turn off some of the injectors to keep it from completely seizing up. A motor ran at 260-270 IS SHOT. It'll only be a matter of time. The resiliency of the head gaskets is GONE, the heads Will expand and distort as the bolts try and hold them down(or strip/pull out) and most importantly, the piston to bore clearance will Disappear and the pistons will gouge and distort the bores of the cyclinders. It'll be Guaranteed to burn oil And lose a headgasket or two eventually. I have firsthand exposure to motors seeing those temps and what the piston skirts and cyclinder bores look like at those temps.... SHOT. The N* may have some advanced engineering
    to some in it, but some space-aged aluminum, steel and gasket materials with abnormal physical properties I Don't see it having. Also, unless these motors are machined out of the factory with larger than "typical" piston to bore clearance to sustain excessively high temps, I so far have not heard any piston "slap"(the piston rocking in the bore) on cold startup. (That is something I will be looking into later...ring end-gap and piston to bore settings of this motor)

    NEVER in all my years have I seen a thermostat mounted on the COOLED/RETURN side of the block. WHY this setup I ask??? Was it engineering "hot-dogging" or just space constraints? I think I remember seeing something about the N* cooling system to be designed with increased passenger compartment heating in mind. That would explain the heater core return temp affecting/controlling the engine's running temp. This also explains why blocking off the heater core lines would cause overheating...the thermostat would Never warm up to open!

    That little device called the thermostat for what little it costs does an Incredibly good
    job of regulating engine temp when it's mounted to "see" the heated engine coolant. WHY "fight" something that's worked So Well over all these years???(and even today still with 99.9% of the vehicles on the road). So far I am Very UNimpressed with any hi-tech-ness to this cooling system. I see Nothing out of the ordinary other than cooled EGR feed ports and an unheard of wrong side thermostat installation. But hey, hat's off to some engineering "feats" to make it happen.

    Car companies regularly give teams of employees a budget to take and use with their skills and creative imagination to produce a product that will catch the consumer's eye, sell cars, and ultimately make the company money. There are some tried and proven design aspects that are typically followed in research and development, but employees are Encouraged to use their imagination to come up with new and exciting designs and discoveries. Hundreds of millions of dollars is "played with" in this respect. These companies also have testing and endurance procedures in place to keep the R & D departments in "check" so that they're designing stuff that will last and are not just awe inspiring to make their bonus's. But these testing and endurance tracks and dynos can never fully achieve real world use as hard as they try. Still to this day ALL car companies still churn out cars that have design flaws. Things that fail prematurely. Some even bad enough to warrant a recall. It's something that will Forever continue to happen. CAD programs and test tracks will forever fall short of actual use. Period.

    I am not trying to cause panic or tick off anyone with what I'm saying here. Nor am I
    suggesting that there is some huge problem with this car as it rolled off the assembly line. I'm just saying I see things here that are Very different from the "norm" of other vehicles of even today. Everything is bound to eventually wear out/decompose/need service. Everything. Nothing lasts forever. But I see some uncommon characteristics here. Some that don't surprise me with the end results. I apologize for walking in here and sounding so bold being a newbie to this board. But another thing that's been raising an eyebrow to me is your "That's the way it is. Accept it." attitude bbob. It's as though you take every person's head gasket/oil consumption problem personally and tell them to just follow the repair procedure and live with it. Helpful, but oddly personal. For every problem there is a reason and a cause. So far I have seen No mention or plight for a cause other than an argument about dex-cool. I am the type of person that likes to nip things in the bud before problems happen. I like things to perform for me and with good peace of mind. And my reasons for posting are not to rip anyone or anything, but rather to inspire some healthy discussions to possibly make things/life better. We all want that I'm gonna venture to say. So I do appreciate your taking the time to comment back and type all that back.

    You mention that I am just becoming alarmed to posts on this board as only seeing a select few people posting their failures. With other vehicles and their associated forums I've been on, typically the big/common topics are performance mods, Audio/Visual upgrades and neat mods/experiences. Random problems and fixes are always there and are just that...Random part failure. But once in awhile you will see a certain vehicle type with an inherent typical problem. Here, time and time again, the big subjects that keep popping up are Head Gaskets, High Oil Consumption and alarming coolant temps.

    I could go on and on, but let me finish this long post with this...

    Lingenfelter and many other high performance/high endurance engine developers have always pushed for lower block coolant temps. So please don't look at me like I have 3 heads. Cooler stats come in almost Every aftermarket mod these days. Even some of new cars coming out of the factory today are running < 195 block temps...And most importantly THEY RUN AT A STABLE TEMP.

    I am expecting differing opinions and comments returned and that is more than fine, expected and encouraged. To this day different engineers will argue one tidbit till the death against each other(say intake port shape for example) and NEVER agree. Each of them spending tens of millions of dollars on R & D in their different companies and each of them coming up with different shapes and port sizes. They are set in their ways and both believe they have the BEST setup. My point is this... some things work better than others while both will work relatively fine. There are those that are ho-hum with the way things are and they accept things the way they are. And that's fine. But let me ask you this...How many of the owners on this board do you think drive around worrying about when/if they'll ever have to end up having to give timesert a call? Do you think that's not something in the back of people's minds? No peace of mind there. As I've said, All of these points I've made can be argued. But me stressing the importance of a stable running temp I Do have to stand up to. I would definitely like to see that in my Caddy. For those of you that Don't think that will increase the longevity of this motor...I'm very sorry you believe that.

    P.S.: Just a little FYI: the OEM thermostat for these cars is a 180. But the engine hardly ever sees/stays at that. It's pretty obvious now why. I Definitely would NOT put an even lower degree thermostat in my engine. Temp swing is what my gripe is All about.

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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps

    Pretty good rant but I think you're just a litle bit late. My '04 CTS with the VVT V6 North* has an analog temp gauge that never budges off the straight-up mid range mark from ambient of -49F to +95F over any terrain. What ever the problem may have been, has been designed out of the newer motors. At the same time the water temp my '95 Ford Ranger 3L V6 wanders all over the place for no apparent reason but with no apparent effect. The temps you make such a point about for North* motors are childs play. My copy of the pilots operating handbook for the North American F82 "Twin Mustang" with liquid cooled Allison V1710 engines lists the normal coolant range as 221F to 239F with 275F as the upper limit. The upper limit for cylinder head temps of air cooled aircraft engines are about 460F at the bayonet probe location. Pratt & Whitney R1830 engines have been operated with cylinder head temps in the low 70's F. and it isn't known if this is the lower limit. These engines were getting times of 3500hrs between overhauls when operated at these temps. That works out to about 700,000 miles. The point I am trying to make is that engine temps can be all over the lot for any number of reasons but what works, works. Much ado about nothing, a tempest in a teapot.

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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps

    Maybe I am missing something here. My 1999 DeVille with 46k runs all the time (winter / summer) at 202 - 210 degrees F. Seems pretty stable to me!

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    blunted is offline Cadillac Owners Enthusiast
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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable T

    Bluemoon : Personally I think there might be some kind of argument made to the effect of what you said but I do believe it's more of a "in theory" on paper kind of thing. Yes I'm sure you might find the set-up of the Northstars cooling a little on the "different" side but do not make it seem that this engines are designed in a way to self-destruct themselves. Many people own these cars with these engines that last a very long time, there is even a post in this section about one nearing 400K. That might not be the norm but these engines do survive with engineering put into them, my temps do jump around and have hit 234 while driving but that is as a NYC driver where this is stop and go and the fast acceleration to pass someone to then shortly come to a stop. Anytime I drive a constant speed in the country or highway the temperatures are not moving constantly until I come to a stop or close to it. As a 94 Eldorado owner.. YES the time-sert issue is on the mind to a degree but I have calmed down with that as well after looking at it from a different perspective. If you do what your supposed to with the cooling you should be ok, I havent heard many people saying their heads blew and that they've been the ones to responsibly maintain that cooling system for the life of the car. It is more like " I bought this car with 1XX,XXX miles and 20 thousand later I blew it" or something to that effect. My car I bought with 59K, and serviced the cooling system right after, to me this means that it came filled with fresh coolant that was good for around 30k or so and there's possibly 29K miles I have to perhaps wonder if the owner bothered servicing the system in. But hey, thats the risk you take and usually people do it while factoring in alot more "questionable" miles. So all these headgasket problems are more what people make of it in my opinion, which is just that.. MY opinion. If you go to the caddyinfo message boards you will see that they recently did a poll of how many people have needed headgaskets and when you see the number of high mileage northstars that are fine , maybe you will rest a little easier as I did. I think the best idea is to do what Bbob has told many people.. "shut your display off and drive the car", it's the great electronics in the car that let you monitor everything going on with it and it turns out to be its biggest enemy sometimes because thats all people do, monitor it and stress every degree that goes by. Also, on the topic of these vehicles consuming oil... YES they eat oil, live with it! So do many other high end automobiles that cost even more than a cadillac, if you wanted something that never ate oil or that you didn't want to worry about changing than why you dont have a Honda is beyond me. For all anyone knows their "reliable" cars might not have the most stable tempatures all the time either, but you wont know because it doesnt have a sophisticated computer in it telling you what's going on throughout the car at all times. Heck, I almost bought a V6 accord cause it was "reliable" but I saw the Eldorado and instantly fell in love and went with performance over reliability. Granted, I have put more money into this car than I would have needed with an Accord, but I would NEVER and will never trade that for the feel and power of this car.. Amen.

  9. #8
    BeelzeBob's Avatar
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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps

    bluemoon....I think you are misunderstanding part of my post. The answer to much of what your second rant addresses is in my first post.

    Look at the Northstar thermostat carefully. The thermostat element is "seeing" the bypass coolant primarily which is the true temp of what is in the engine. It is not just seeing the "cold" coolant coming in. The cold coolant into the engine must mix with the high bypass flow before the stat thermostat element sees it...so...the stat is seeing what the engine is going to get for coolant temp. Exactly what you (and the engine) want it to.

    Be carefull of what "Lingenfelter" wants and what works on the dragstrip for instantaneous power for a burst reading. Passenger car engines are designed to operate under a hugely wide variety of conditions....not just make power down the dragstrip or pull a big number on the chassis dyno. You are not going to see Lingenfelter's or anyone's hot rodded engines make the kind of long term durability and endurance of the production engines. Cool stats are admittedly "good" for power for burst readings and helping with detonation. But passenger car engines must also have PCV systems that work, pass emissions that are far more stringent than sticking a probe up the tailpipe for 2 minutes, cool pulling trailers and heavy loads, work in -40 weather going to the store as well as idle in Phoenix city traffic at 120 ambient. What "Lingenfelter" or other tuners expose rarely meets the requirements of the general population.

    I agree that very high coolant temps can aggravate detonation and preignition tendencies....but....that is at the far reaches of the elevated coolant temps. We often talk about what the highest temps can be and how hot can it get without hurting anything, etc....but.....most of the cars most of the time run around the 210 range very repeatably. The excursions to the very high side simply are the far reaches of the systems capabilities...not what most people experience most of the time. Yes, the knock sensors will start to pull spark out when the engine reaches 250 and 260 degrees to prevent detonation....but.....the compression ratio and spark advance was carefully optimized to allow operation at MBT spark (optimum spark advance for power and torque) AT THE COOLANT TEMP RANGES NORMALLY SEEN. In other words, the engine will operate with no knock sensor induced spark retard at 210-225 with no problems at all. IT WAS DESIGNED TO DO THAT. And it was tested and calibrated under those conditions to make sure that it will. If not, the compression would have been reduced. There is FAR FAR more to optimizing these packages than the one dyno pull you read about in Hot Rod magazine!!


    I do understand your comments about the coolant temperature swings and the damaging effects....I thought I addressed that in great length in my post. The swings can have a deleterious effect if they are not controlled and if the engine is 'seeing" the shock of a coolant temp swing suddenly. This is mitigated , as stated above, by the high flow rate system and the huge bypass flow that mixes with the incoming coolant to keep the engine at ONE temperature and to allow it to change as one piece due to the high coolant rates flushing thru it. It warms the cold spots up rapidly and cools the hot spots rapidly so as the keep the engine globally at an even temperature and allow it to globally change temp as one entity.

    GM does extensive "thermal shock" testing of the engines by flushing hot (very hot...like 258 degrees F) and cold (very cold...like -20 degrees F) coolant thru the engines to "work" or distress the gaskets as much as possible to accelerate failure modes for testing purposes. The Northstar engine excells at this type of testing due to the high coolant flow rates forcing the global temp of the engine to change as a single entity rather than part of it gettting hot and part being cold...or vice versa. I do this type of testing regularily so I see the results constantly and the Northstar does very very well at it.

    Things are different on the engine...?????.....uhh....welll....uhh.....yea. It is all aluminum, it does make a lot of power and rev hard, it doesn't have pushrods, etc..... Things do change. Look under the hood of any GM car and the competition and things are not llike they used to be. That is a good thing. Not something to bemoan.

    Inlet side stats a poor or questionable design....??? They are very common these days on modern engines. Look around. They are not an engineering exercise. They are done because they do a better job of modulating the coolant temp than exit side stats do despite your theories to the contrary.

    Realize that you may not be "used to" temperature swings but many of the temp gauges that you have used over the years are very "dead" around the 200 degree operation point so that you just do not see the coolant temp swing. The gauges are damped (deliberately) to prevent the customer from worrying everytime it moved. Sounds like you need a damped gauge. Your 96 is a particularily active gauge and digital readout due to the desire to provide accurate and instantaneous information. Generated lots of complaints because many customers (like you) get worried if the gauge moves one needle width off center or wags around at all. Later model Cadillacs have the coolant temp gauges and digital readouts "damped" considerably to prevent this issue......true.

    You are missing the point I made earlier...... by lowering the thermostat operating point you have INCREASED the range and likelyhood of the coolant temp swings that are seen. You have made the situation worse with the colder stat. That is your fault, not Cadillac or GM or the engineers that designed the system... Normally the upper end of the temp range (in normal, 99 percentile conditions) is dictated by the fan turnon point and the lower end by the thermostat control point. If the thermostat active control point is 210 or so and the fans turn on at 225 then it is onlyl 15 degrees. Put a 180 stat in there and the coolant will cool down to 180-190 with the fans on and then warm up to 225 when they turn off. NOw you have created a 35 or 45 degree range. PUT THE OEM STAT BACK IN. It is designed for the system to operate that way. I can commiserate if you want to change it for change sake....but....since you cannot reprogram the fan control point you really need to let the sytem work like it was designed....not like your misguided , preconceived notions dictate. Realize that the engine and cooling system was optimized for a variety of conditions and to operate at the most efficient point for the engine. It was NOT designed for you to be able to modify it easily...or at all. Aftermarket modifications to the sytem are not something that the engineers even consider. So, if it is hard to modify like you want......tough. That was not one of the design constraints.

    Trust me, there are a lot of pretty smart engine cooling engineers and developement engineers working on those packages. And, as stated, the Northstar engine received tremendous attention to the cooling system by those engineers. Regardless of your background, you have some catching up to do to understand how the sytem operates and what needs to be done to "improve" it.


    AS far as engines living better when hot....I see the examples daily from the factory testing. I know that they live better running the higher coolant temps. And I see the results from the field of running the higher coolant temps of todays engines. The engines look much better and live much longer and have far far fewer crankcase oil deposits and problems of that type. As far as oil oxidizing at higher coolant temps....cold coolant temps are as deleterious to oil more than higher temps. Getting the coolant above 212 boils off the junk sooner in short trips which the general public does frequently. Oil oxidzes severely and becomes a concern above 305 degrees F......far far above the coolant temps that we are talking about.

    Talk about another misconception....most people think oil is supposed to NEVER get above 200.....LOL......we always want to see the oil at 230-240 to keep the water and heavy end hydrocarbons boiled out of it and to improve the fuel economy. Modern oil is MADE to run at those temps. You are not helping it or the engine by keeping it colder.


    I just believe that you are so firmly convinced that you have discovered a major design problem here that you cannot see what it really going on the system. It does work well. It works better than systems of the past and, as indicated, pioneered many items that improve the performance of cooling sytems that are seen on other cars today. It is designed to operate at higher coolant temps for longer engine life (in the real world from Fairbanks Alaska to Death Valley, Calilfornia) and it does it quite well as long as it is maintained and not modified. Don't blame the system for poorer perceived operation due to your colder stat mod.


    The bottom line is that if you read thru posts on the previous pages you will find pictures of Northstar engines torn down with nearly 200K on them. The pistons look great. The cylinder walls have the original facotry honing marks in them. The valve seats and heads are perfectly fine. Timing chains and sprockets and cams are perfect. etc..... Not bad for an engine that the engineers botched the cooling system on I would say.

    Yes head gaskets rise to the top of the most common failures as the engines age. For 150k to replace the head gaskets and drive another 150K is pretty good I would say. Compared to the "old days" where engines needed rebuilding at 100K and the cylinders had such a ridge at the top that you couldn't get the pistons out the Northstar lives and wears pretty well I would say. Every engine has maintenance of some sort required as miles build up. Seems the Northstar needs an occosional head gasket. Lexus engines need timing belts. Cost is the same. Break a timing belt and you buy a new engine. Loose the head gasket and you get plenty of warning, it is easily repairable and the engine requires no other work.


    By the way.....you are completely off the mark with the idea that the cooling sytem can "run away" at some point. And the idea that an engine that is run at 260 - 270 being shot is ludicrous. Completely ludicrous. I have seen many many engines run to those temps during testing...some for extended periods of time (like as in hours) and they are fine. As long as the engine has coolant in it and it wetted it is fine. Your idea of what is going to cause a failure is not reality. Having worked on the developement of the limp home mode I do take a bit of offense to the cheap shots you take at it. The engineers realized early on that an all aluminum engine was going to be very susceptable to damage if overheated severely so the limp home mode of cutting out cylinders to allow the engine to "self cool" was invented and developed. There was one Northstar engine that spent a solid 10 months on a dyno developing that system to the point that a Northstar can literally run with NO COOLANT IN THE SYSTEM for 50 miles at 50 miles an hour to allow the customer to reach a safe spot in the event of a system failure. It works. I have left work with a "dry" Northstar many times, driven 40 miles home, parked and went into the house, started the car the next morning and drove 40 miles back to work....with no coolant. The engines run fine when filled with coolant afterwards. This has been documented by several major santioning organizations and by two separate magazines that ran their own "validation" tests (one by driving from Yuma to San Diego with no coolant) to prove us wrong and in the process wrote excellent testimonials to the success of the system.

  10. #9
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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps

    Among engineering professionals, GM engineers are regarded as being the finest automotive engineers in the world. They have pioneered virtually every device commonly available on cars worldwide today. From the self starter, to Ethyl gasoline, to power steering, to automatic transmissions, to recirculating-ball screw actuators. The list goes on and on. The idea that someone is going to reverse engineer and reinvent the cooling system of a North* by peeping in the holes with a flashlight is pretty far fetched. If Bbob tells me how and why it works like it does I am ready to believe him and go on to the next issue.

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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps

    GM engineers are not all gods however. Chevrolet had developed an automatic transmission for Jim Hall to use in his Chaparral sports cars. This gave a free foot to the driver that Hall took advantage of to control a huge wing on the back of the car. The car was unbeatable. Ford wanted a comparable transmission the worst way and decided to hire the responsible engineer away from Chevrolet. Chevy management got wind of this and cooked up a practical joke. They leaked the name out of the supposed engineer but in fact it was a dud that they were ready to can for incompetance. Ford hired the guy and put him to work leading the design team. The resulting transmission was put in a Ford GT40 variant called the "J" car. At 220MPH the transmission seized up resulting in the death of Ken Miles, one of the finest race drivers of the times. In the end the Chevy transmission turned out to be a beefed up "peanut butter drive" Powerglide.

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    BlueMoon is offline Cadillac Owners Member
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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps

    I don't believe I was taking pot-shots. I was just stating some very visible aspects of this cooling system and looking to spark some thought into better longevity of this engine.

    My background is NOT a Hot Rod magazine reader. That I found to be an outright insult. Especially since you don't know who I am or where I'm coming from. I'm guessing you took that assumption from the Lingenfelter example. But it was just that... an example(of many). As I stated in my above post the BIG 3 at this moment are rolling cars out that have <195 running temps. So I wasn't just talking about ONE guy doing something in my previous post.

    If you wanna talk about Lingenfelter, he doesn't do just burst and dyno run research. And he IS involved with passenger vehicles and endurance. Even at GM.

    Your mention of dampened and/or non-linear gauges is just plain CROOKED ENGINEERING. I am just outright shocked that you said that. It's a cover-up. If you don't want the public to see what's happening then it should be an idiot light. Temp and oil and volt gauges are just that...gauges. They show the variations and people pay extra to see those instead of the idiot light. They WANT to know what's going on. The only thing you would ever wanna damp is the fuel gage...and for obvious reasons. I have a feeling already that some of the temp gauges in these cars have been mocked up to be non-linear.

    Until there is some new law of physics that's discovered where fluids aren't used to remove the by-product of combustion(heat), coolant is circulated within an engine block until the desired running temperature is reached, then the coolant is released(and regulated) by the thermostat to be sent thru the radiator. That's how it IS now and Has been over the years on 99.9% of the vehicles out there. By you stating that the stat being located to release HOT coolant at it's rating like this is inferior, then the billions of cars and car manufacturers who design cars would have migrated to your/this setup of the stat being mounted in the cooled return inlet to the block instead. Are All(or even most) of GMs vehicles now cool side stats???...No.... So I don't see where you are coming from saying cooled side Is the "norm". THE HOT side IS THE NORM. SO YOU ARE FLAT OUT WRONG! It doesn't take a "Hot Rodder" to see which way would work better too.

    I don't doubt you one bit that TONS of money and work and man-hours went into making a thermostat work on the cold side. I would expect it to. But I Do have to laugh at your off-the-top-of your head figures you threw at me in an earlier post about the water pump flow numbers. YES, I'm Sure the water pump flows that amount. It NEEDS to. And I'm not at All impressed that the water pump can pump on a 6500 rpm motor versus a 5500 motor. That's the operating range of the motor so IT HAS TO. Again, my references are to the stat. Not the pump.

    I have to say that I am taking an irritation to this subject and will need to end input to this post because I can see personal pride is getting in the way of open discussion and possible improvement. I was unaware going into this post that you had a hand in the devopment of this cooling system. So I can't fault you for standing behind your product citing millions of dollars and lots of research. GM and other large companies put millions of dollars into research into ALL kinds of things. That doesn't mean they are Never wrong or that there isn't or won't be a better way to do something. I could site examples but that would be sheer offensive and that is not of my intentions at All. If this was the ideal way then it wouldn't have changed at all in new models. Period.

    I can also see now why the fan turn-on temps are so high....because too cold of a radiator return temp would cause excessive thermostat closing/cycling. And there you have it... 40 degrees of Swing. The system WILL run better with the AC going too because the fans will always be on(and the condenser will add a little pre heat to the radiator too). I can see why the compressor is on so much now too.

    I personally see no way to improve on this setup the way it is other than moving the stat over to the proper side. So you are right in that there is NO room for modification in this configuration. This backwards way is working as well as it possibly could.

    None of this is magic or something people would have a really hard time understanding. At times you make people that ask questions feel like they could Never comprehend the setup of the N* cooling system. Yes, there is some initial head-scratching to those used to the conventional cooling system technology. And it Does take a little bit of looking to see how you/they heat up a thermostat that has cold/cooler coolant flowing thru it. But all cooling systems have their basic components and they all no matter how they're mounted all strive to do what they need to do...remove the heat and keep a stable running temperature. When people
    want to get into the "meat" of things you at times just throw miniscule engineering "stats" at them just to get them to stop in their tracks. I'm surprised you didn't throw the internal block coolant surface area at me to be honest too. When I mention 40 degree block temps swings you tangent off into flow numbers and hot-spots within the engine. Hot spots and internal temp stabilty are things that engineers fight with to get coolant in between the valve stems and alongside the intake ports and combustion chamber etc.... And they are fighting against the space constraints of the fasteners and the ports, and the plugs...etc...etc... If you wanna talk about hot spots and design, why don't you talk about the inherent properties of All engines where the first cylinder that sees the coolant is the coolest and the one at the end of the line is the hottest, is usually the first to detonate, show signs of wear and/or fail. A couple of degree temp changes in spots within a cylinder head is NOTHING compared to everything "globally" moving up and down 40 degrees. These cars do have inherent early head gasket failures. So far you have not given a reason why personally or from a hands on research standpoint for a cause other that they just wear out like a timing belt. If you are that into this motor than I would kind of expect to see some extended research and data into this subject. But I see you say Nothing of cause or effect other than to discount dexcool as the problem. So I still feel like you're sidestepping getting into the meat of things.

    I don't doubt at all that you have run these motors for periods of time without coolant. Like I said, I am not impressed that this motor can run regulated by the computer without coolant in it. If that helped sell more cars, then the added software in the computer was worth it. All it does is get you closer to the tow truck. But like i said, I will BET you one on one that that motor will have a head gasket/oil consumption problem in the not too distant future after that. The expansion rates
    of aluminum, steel and gasket materials are all the same no matter whose assembly line it rolls off of.

    Something else that you misunderstood what I said....
    I said I am NOT changing the stock thermostat! The stock thermostat is 180 FYI. I'd think you would know that. It's in the factory parts book and it's even stamped in the housing of the stat(I'm looking at one right now). And as I said this engine Does not and Will not ever run at that temp because of this stat & fan design. I'm NOT gonna make it worse by trying to go lower! I'm looking to get AWAY from temp swings. You're Not reading what I wrote.

    AS I said, I don't see you agreeing with any suggestions for improvement on account of pride. So i'll leave you to rubber stamp the Bars Leak in the lower hose and the timesert procedure.

    I think you can tell by now that I am not a mechanic standing around with a flashlight.

    It's very obvious that card-blanche was used in the N* development. Aluminum Four valve per cylinder V8's with gyrotor oil pumps, etc are hi-tech, efficient, Expensive and just plain bad-ass. So you can see that GM was passing out alot of money in development at the time. I just think that they/you went overboard on the cooling system and tried to come up with something new and exciting. Just what it see.

    I think it's great that you are on here countless hours helping people and giving them
    invaluable tips on repairs, shortcuts and just plain being nice. You are obviously a very
    nice person. I don't wanna ruin that for others by making you mad. So I am gonna keep my further opinions of the cooling system to myself. You are by far more of an asset to this board that I am. Don't get me wrong, I think the Nothstar engine in itself is something to be proud of. I LOVE it, I love the Eldo body style and I'm gonna be looking into making it's running temp more stable. It's just sad that pride is getting in the way of things now. But I do understand.

    It was nice talking to you.

  13. #12
    BeelzeBob's Avatar
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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps

    bluemoon....in case you are still listening....

    Nothing personal here at all. Just trying to pass along the facts of what went on in developing the engine and cooling system so that you can understand what works and what doesn't and why.

    The issue with an exit side stat is that the stat sees the "hot" water at the thermostat neck. So it opens....and "cold" water from the radiator enters the engine at the far end of the system. Most all systems operate such that the water pump picks up the cold water at the inlet of the pump, pushes it thru the block and then up into the heads. From the heads the coolant is collected and routed to the thermostat. Once the stat sees the hot water and it opens it will flow the hot coolant out of the system until the slug of cold water flushes thru....then the stat starts to close....until that slug of cold water becomes hot water and then the stat opens and the cycle starts all over again. This happens. Worked on cooling systems too many years and seen it too many times on too many different engines. To prevent this, there is always some coolant bypassed back to the water pump inlet to create a positive flow past the stat even when it is closed so as to minimize the thermostat cycling. Look at the coolant bypass circuit on the transverse 4.1/4.5/4.9 pushrod Cadillac engines...that is specifically what it is designed for. All other cooling systems that use exit side stats have some sort of bypass or thermostat bleed to prevent this cycling. Many stats have a simple hole in the paddle to allow a "bleed" of coolant flow to keep some flow past the stat even when it is closed. This obviously hurts warmup performance. When you have a clean sheet of paper and can design the cooling system with the stat where you want it is much easier to put it on the cold/inlet side, design in a coolant bypass circuit that flows over the stat thermostatic element and control the flow of water to the rad that way. In that fashion there is no need to sacrifice cooling system performance or warmup rates by dumming in a bleed or "leak" in the system , nor do any extra external plumbing, to achieve no stat cycling and maximum warmup rates and maximum cooling system performance.

    In actuallity, there are several different GM engines and vehicles with inlet side stats.....yes. There have been for years.

    Part of the issue is the idea of "right" and "wrong" and the concept that one way must be THE right way. Both ways work. An exit side stat can work fine and an inlet side stat can work fine. There are advantages and disadvantages to both. Most "pros" end up on the side of the inlet side stat...but it requires an engine cooling system and water pump and pressurized surge tank to work correctly so it will not show up on engines until they are redesigned to incorporate the system fully. An inlet side stat does allow superior thermostat cycling performance and provides this control with no loss of warmup performance due to unnecessary bleeds or bypasses of the stat. I never insinuated that the cold side stat was "the norm"...just that it can provide superior cooling system performance..if it is designed correctly. I am NOT wrong on that fact. I understand that most cars "that you are likely familiar with" have exit side stats....I have a couple of old muscle cars, too. But the inlet side stats work better. I doubt that most of the "hot rodders" are ever going to understand this as they do not generally understand what a cooling system has to do or how it really works...LOL.

    Most "hot rodders" still think you have to slow the coolant down so that "it has time to pick up the heat and time to release it in the radiator."...LOL LOL This is so far from the truth that it is rediculous but it is still repeated to this day in hot rod magazines of all type. So...I would expect a "hot rodder" to think an exit side stat is better "because that is the way it has always been".....duh...


    The radiator that rejects the heat does not care where the stat is at.....it just sees the flow. The coolant circuit to the rad can be controlled on the inlet to the rad circuit (a hot/engine exit side stat) or on the exit of the rad (the cold/water pump inlet side stat). It makes absolutely no difference to the rad. The flow is the same. Kind of like interrupting the circuit for the light bulb.....take away the volts or the ground and the bulb goes dim.

    If you are not impressed with the 105 GPM flow rate of the Northstar water pump at 6500 then it is obvious that you know little or nothing about cooling systems in cars. That is a major major amount of flow increase compared to systems prior to 1993. It definitely broke new ground for flow rates, water pump design, etc... for engine cooling system. I actually did some of the early work in the mid 80's regarding establishing the bogey flow rates required to thermally stabilize an engine making that level of power. We did developement work using two and three water pumps cobbled onto an engine to get sufficient flow. The pumps and engines you gained experience with that are made prior to 1993 pump WAY WAY less coolant. Way less. It took a lot of time and development to get a water pump on an engine that would flow that level of coolant. The old pumps will just not do it. Speed them up and they cavitate and stop pumping. This is also what led to the pressurized surge tank to pressurize the water pump inlet to prevent cavitation.

    I personally knew John Lingenfelter before he passed away. GM has worked closely with him on may projects...all high performance related BTW...nothing production related. I personally helped him with the valve train on the Ecotec motor that they were running in the drag race series for sport compact cars....the one running 40 PSI turbo boost that was blowing the intake valves open...LOL. I know exactly what kind of cars and engines he builds. They make some high performance stuff....but.....not the kind of stuff to run hundreds of hours of dyno endurance without breaking and the power numbers that they come up with are indeed flash dyno readings on a quick pull or a transient pull on an inertia chassis dyno. Lingenfelter's organisation does excellent work (my neighbor finished the One Lap with a Lingenfelter CTS-V and owns the supercharged CTS-V that was in the Car and Driver shoot out several months ago...) but they build race cars...not stuff to haul butts for hundreds of thousands of miles. Sorry to burst your bubble.

    Crooked or not....that's the way gauges are set up.....LOL. Even some of the very expensive aftermarket gauges are heavily damped. I have a Autometer mechanical coolant temp gauge on my garden tractor that I installed (an engineer never trusts the engineers that designed the device so I can relate to your feelings.....seriously). I also installed a quickie, instant response K type thermocouple for a temporary check of the gauge calibration. That Autometer gauge has enough damping in it so that it does not respond to the 8 degree F thermostat cycling that I see with the thermocouple!!! So.....the things you take as gospel may not be.....be aware.

    If you really want to be livid over passenger car OEM gauges I will tell you that there is more than one application where the oil pressure guage is really a dummy reading. Purely for show. It is fed a signal/data generated by the PCM based on oil pressure, coolant temp, etc. The engines do not even have an oil pressure sending unit on them...!!!!! Purely fictious readout. LOL LOL True. It looks and responds exactly like the engine oil pressure should...but it is just a generated signal. PS...there is an idiot light also....

    The AC compressor run time has nothing to do with keeping the fans operating....duh....think about it. If that was the simple goal then why didn't we just make the control system run the fans regardless of whether the AC compressor was possible or not??? It would have been much easier to do this than run the compressor too much as you imply.


    BTW....your personal pride is getting in the way of future conversation...not mine.....LOL.... I try to provide as much fact as I can and insight into how the systems were designed so that people can understand what all is involved. If someone cannot grasp what the significance of a fact or figure that I provide is about then it is not because I am trying to snow them....maybe they really don't understand exactly how the system works....

  14. #13
    blunted is offline Cadillac Owners Enthusiast
    Automobile(s): '94 Eldorado , '12 CTS Coupe
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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable T

    Well I must say I have learned a nice amount from this thread, thanks in part to Blue being so stuck on his preconcieved notions that Bbob went and explained this interesting system with great detail. Blue, I wouldn't take the way things are said personally, they are just direct and to the point answers which is what you should expect from a cadillac engineer! If your detecting some sort of tone in the statement maybe its from him having to constantly re-iterate things to everyone and being challenged by people who think they know these vehicles better than the person who helped create them. Bbob is always helping everyone on the forum and for that I must say Thank You! If it wasn't for this forum I wouldn't know my head from my ass when it comes to my Eldorado.

  15. #14
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
    Automobile(s): 2006 STS V8 AWD, '95 Ford Ranger
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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps

    Bbob, is there a peer reviewed paper available on the North* cooling system? It seems very simple to me; much like the blended flow systems used to regulate the temperature of a radiant floor heat slab.

  16. #15
    LCLCLC is offline Cadillac Owners Fanatic
    Automobile(s): 2005 Deville
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    Re: High Oil Consumption, Pulled Headbolts, Blown Head Gaskets, Bars Leak, Unstable Temps

    Kind of a minor point to inject into this discussion....

    I was really impressed with the oil pressure that my 94 Ranger 4L kept. It went right up to about 3/4 gauge. And stayed there. And after running on a hot day and going to idle, by golly, it still kept 3/4 gauge. I thought, hummmmm, this didn't seem quite right to me. But maybe those Ford engineers have a high volume/pressure oil pump, with internal bypass valves so it will always keep a nice high pressure.

    Then I started reading on the internet. What do you know, this gauge is really just an attractive idiot light. The oil pressure sensor is an on/off switch calibrated to about 5psi. Anything below, no gauge, anything above gives 3/4 gauge. I don't know exactly what year they started this, but it continues in the new models also.

    I felt kind of like the singer of the song 'Angel In A Centerfold', when he sees the centerfold picture of the girl he always idolized in school.....

    I wonder how many other Ford and other models' oil gauges are also on/off switch displays????

    But, still, "I Love My Truck". Just another small eye-opener about how the world actually works.

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