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99 SLS Engine Runs Hot - Looking for Advice/Recommendations


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A) I think you said knock sensors allow the engine to adjust for knock (I agree) and that the engine can do nothing about the combustion point of a specific octane of fuel. The latter statement is presented as if to refute the former, but does not; the fact that modern engines can adjust in fact allows them to run higher compression with lower octane if needed without knocking.

B) please refrain from personal attacks on other Posters ("it is obvious you are clueless when..."). I know many forums allow or encourage that type of jousting but it is not within the terms of usage here.

Bruce

2023 Cadillac CT4-V Blackwing

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It is obvious you are clueless when it comes to compression ratio, gasoline, and octane.

And you can't read between the bullshit lines the GM Engineer is feeding you.

Regular unleaded is 87 or 89 octane. It will detonate in an engine with a compression ratio of 10.3:1 or 10:1. The timing event that the computer controls will have no effect on the combustion of the gasoline, thus rendering computer aided retardation of the timing (knock sensor included) USELESS.

GM thinks 92 octane fuel is regular? Not in the real world....

The type of engine has NO BEARING on the fact that gasoline needs to be 'tamed' (so to speak) inside of the combustion chamber. The cheapest way it is tamed is by adding octane. The more octane, the more tame, and the more likely it won't detonate in a high compression engine like the Nstar - or ANY OTHER high compression engine.

Do you know what causes the "knock" that a knock sensor is searching for?

I remember when engines (even fuel injected ones) actually ran without the use of computers. What the heck, Sprint Cars don't even have a battery..

It matters not how many computer controlled devices are attatched to an engine - or how many computer designs are rendered. The mechanics of the crankshaft, rod, piston, piston rings, and the explosive power of gasoline remain the same.

I can't believe I'm still replying to this topic....I hope mostfocused' 99 sls overheating problem is solved

Tell me why GM puts a knock sensor on these engines then if it is so useless as you claim? Neither GM nor any other automaker is not going to add components to an engine unless they have a function. Where in any of these posts did anyone say that "GM thinks 92 octane is regular fuel" Tell me why the 2000+ Northstar engines specify 87 octane regular fuel and run perfectly fine on it - without knocking. I presented the facts (which you seem to ignore because they are contrary to your opinion) on how the engine combustion chambers were redesigned to use regular fuel without knocking and because it does not meet you preconceived notions, you resort to personal attacks. You had better read the terms of this discussion board that you argreed to when you signed up. I think you are on the wrong forum.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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TJ95 this thread was started by a guy who was needing help / guidance about his 99 SLS that had a overheat issue. The thread now has morphed into you giving us a lesson on rocket science and STUDS that your pushing hard. I have been working on this motor the Cadillac Northstar for over 20 years and I can confidently say I have fixed hundreds to a thousand of these engines using let alone Timeserts, Norms inserts, 10 plus years before STUDS appeared on the market.

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Running your Northstar hard will not cause problems.

I do recommend that you service your transmission if you have over 100,000 miles on it, particularly if you plan to run the car hard.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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KHE - I did not say knock sensors are useless - If I implied that my mistake. I did say the combustion of 87 octane gasoline (or gasoline not rated to combust at it's proper time inside of a 10:1 compression engine) will happen BEFORE any spark happens inside of the combustion chamber - thus taking the computer and all it's related sensors (knock sensor included) out of the problem and rendering them useless. Another way to put it, if the knock sensor is doing it's job, there is something wrong - and that something will cause serious damage if not corrected. If your engine has 10:1 compression, and you run 100% 87 octane fuel, it will damage all the stuff I have already mentioned - for all the reasons I have mentioned. And I am sure barczy01 will be happy to fix it for you.

Compression ratio is compression ratio - no computer, knock sensor, or redesigned combustion chamber can change that.

barczy01 - there is a reason that just one person (you) has worked on thousands of these engines for the same problem, which indicates a design problem. After the horses have been out of the barn for many years, GM would never say that - would they? Fixing them is great, but finding the flaw seems to be so illusive.

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KHE - I did not say knock sensors are useless - If I implied that my mistake. I did say the combustion of 87 octane gasoline (or gasoline not rated to combust at it's proper time inside of a 10:1 compression engine) will happen BEFORE any spark happens inside of the combustion chamber - thus taking the computer and all it's related sensors (knock sensor included) out of the problem and rendering them useless. Another way to put it, if the knock sensor is doing it's job, there is something wrong - and that something will cause serious damage if not corrected. If your engine has 10:1 compression, and you run 100% 87 octane fuel, it will damage all the stuff I have already mentioned - for all the reasons I have mentioned. And I am sure barczy01 will be happy to fix it for you.

Compression ratio is compression ratio - no computer, knock sensor, or redesigned combustion chamber can change that.

barczy01 - there is a reason that just one person (you) has worked on thousands of these engines for the same problem, which indicates a design problem. After the horses have been out of the barn for many years, GM would never say that - would they? Fixing them is great, but finding the flaw seems to be so illusive.

Yes, you did state that in the third sentence of your post in post #23 in this thread. GM Recommends 87 Octane regular fuel for the 2000-2011 Northstar engines - it states that right in the owner's manual. The engineering behind that was posted, yet you still keep repeating your rhetoric from 1950's engine design. That is your OPINION, it is not fact. If the engine would be damaged by running regular fuel, there is no way GM would recommend regular fuel. Consider the warranty effect (and the legal ramifications) if something was recommended that was catastrophic to the engine.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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There are thousands of 2000-2011 Northstars out there with 150,000 miles or more on them burning 87 octane and they have never had a head off!!! My uncle had a 95 Deville and he never ran anything but 87 regular and it had 150,000 on it when he sold it. Never had a head off!! These are facts Jack!!

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Head gasket problems in Northstars with under 100,000 miles on them or less than about seven years old are very rare.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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93-95 before dexcool, head gasket issues are not as common. 1996 was just the beginning of a long very bumpy road for GM. Dexcool has plagued more problems with Chevrolet, Pontiac, Buick, Cadillac than one can fathom. Dexcool eats head, intake and any plastic gasket in a cooling system that isn't maintained. We might never know what the exact issue for the threads pulling out of the block is but a head bolt torque of 30 ft lb, 70 degrees, 60 and 60 degrees again, is just silly and made to fail over time!

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I have been changing my coolant every 4 years religiously on my '96 Deville, in addition to saying a prayer to the head gasket Gods. Over the summer of 2014 it was changed last - and for the first time without adding the baars powder. I will add it into the radiator in the spring of 2015. I am afraid this time that stuff will clump and foul my surge line. So far after a few hundred miles, it still looks like new, and there is no smell of exhaust or gas from the surge tank. I never ever heard my cooling fan run. I will say a prayer to the cooling fan Gods that this fan will run if its ever needed. Its been sitting unused under the hood for 18 years.

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Having not found a reply from mostfocused (op) it seems ok to turn this thread into whatever it has morphed into. :glare:

barczy0, can you explain your statement please, about the head bolt torque. I am in no way arguing your statement, but as a guy that does his own repairs, I would like an insight. I read here daily for my own knowledge and often receive differing opinions on many things and wish to make my own opinion of ideas put on here. Very few things in this life are actual proven facts. They are only facts until proven otherwise. I find it unbelievable that anyone is intentionally building a head to fail. So the engineers obviously thought they had it right. Factory engineering can be improved I know, so your thoughts please.

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GM's torque specs too much for the threads to hold overtime and or multiple overheating cycles. Even under warranty in the mid 90's for oil consumption, GM advised us at the dealer to re-ring the engine first. Going back together the threads would pull on the last 60 degree turn at times and then timeserts were installed in the block. I will tell you guys from 50lb pounds and torquing to 60lb pounds it only a 30 degree turn of the head bolt, so just imagine torquing the head bolt another 120 degrees or so. GM created their own little problem on head bolt torque and it was made to fail sooner or later. I believe these engines were only made to take the head bolts out one time and that's it. After that, it fatigues the threads and rears it's ugly head of a head gasket issue and pulls the threads from the block overtime. I have developed my own method in the mid 90's and still to this day I use it and I have had 0 issues with my work. If I have had an issue it would be all over the internet.

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