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Hey guys.. 2003 Seville SLS.. Always runs 1 click above halfway on the engine temp. Today in NJ it’s about 90.. I was sitting in traffic for maybe 15 minutes at idle with air on and I looked down and noticed that my temp had risen to about half way been halfway and the first bar. Traffic started moving again and within 50ft temp went back to normal.. by then I was home. Is this cause for concern? I’m tempted to go back out there and let it idle in the heat to see if I should be worried
 

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So I just went back out to my driveway after about 5 min of sitting. I didn’t move the car just left it in park and watched the gauge move up 2 clicks above halfway, then watched it drop back down to halfway
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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Re: Well now I’m slightly worried. Or should I be?

No problem. As Vince posted, pretty normal. Read the cooling system stickies for your fan sequencing and how they operate in traffic and with A/C set.
 

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Discussion Starter #6
Looking at the pic you have posted it usually always runs at 215 always today it went up to 220-224ish which has never happened and caused me to be concerned but then I felt a little better in my driveway when I watched the needle drop back to 215. I’m assuming if it was my HG the gauge would keep climbing rather quickly
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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Re: Well now I’m slightly worried. Or should I be?

If the cylinder block head bolt hole threads have failed, causing loss of head bolt clamping pressure, then exhaust gas blows past the fire rings and overpressurizes the cooling system, blowing off coolant, causing loss of water pump flow, causing overheat conditions.

The fire rings are not elastic like the soft head gasket material - once compressed they require undying clampng pressure to contain the combustion pressures - remove that clamping pressure and leaks occur.

IF the bolt hole thread failures occur the most elegant, strongest repair is one-piece studs - with HD inserts and studs/new head bolts a close (close) second.
 

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Discussion Starter #8
I just went back out and let it idle for another 10 min straight. Sat in the car and every few min the temp would go 2 clicks about halfway then drop back to halfway. I’m assuming all is ok for now
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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Hood open, observing the fan on/off sequencing ?

215 degrees at long-term idle, A/C off, is of no concern. Disgustingly normal.
 

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Discussion Starter #10
I didn’t open the hood but felt like I could feel the fan kick on. I had the ac on. Stayed at about 215ish (always runs 1click slight click above 12” even in winter). Went up to about 118ish every few min while Idling then would drop down to about 215ish
 

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Discussion Starter #11
It may have always down this in traffic I just happened to notice it tonight while in traffic and I’m always more mindful driving a N* when it’s hot out. My other 2000 Deville never once went above 1/2way but the gauge on the base deville is also only a bar diagram not a gauge like the Seville
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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Heh, heh........ the hotter the better........ a 95 degree day is perfect for running the living dog snot out of the STS.

Truth. Don't sweat the small shit and enjoy the car. Fortunately for me, Caroline County is rural rural and the long farm roads allow some fun exercises....... both straight and twisties. Yes, pushing 80 with a short stick advises me to play it smart - I still highly value my quivering pink ass. But the car is so damned much fun to drive.
 

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Master of the Dark Art of Diagnostics
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Looking at the pic you have posted it usually always runs at 215 always today it went up to 220-224ish which has never happened and caused me to be concerned but then I felt a little better in my driveway when I watched the needle drop back to 215. I’m assuming if it was my HG the gauge would keep climbing rather quickly
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Looking at the pic you have posted it usually always runs at 215
that's actually a little warm - but certainly within "normal range"

you might take a close look for some air flow restriction -
stuff on the front of the condenser - or stuff packed between the condenser and the radiator -
 

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Discussion Starter #14
I like this Seville SLS but my Deville was faster especially on Highway runs. I notice the difference between the 300hp and the 275. In between the Deville and this Seville I had a 98 Continental with the “intech” 32valve 4.6 cobra motor that was no slouch either. I hate the fact that this Seville is my only car right now, I need to go buy a second car, I usually like to have Atleast 2 vehicles Incase one doesn’t start
 

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Re: Well now I’m slightly worried. Or should I be?

Actually, what you notice is the not the 300/275 hp - it's the 3.11:1 final drive of the 275 hp vs. the 3.71:1 final drive of the 300. Same reasons why a Chevy with the same engine will be "faster" with a 4.11 than a 3.08 - the engine gets into the power band quicker with the high rear ratio.

A STS/DTS/ETC will slightly out-accelerate a SLS/DHS/ESC - but put that 3.71 final drive in the 275 hp car and it will slightly edge the 300 hp - in a 0 - 85 mph run.

Not true in all cases with all engines with all cars - but holds true in this particular Cadillac car/engine matchup.

FWIW the 300 hp cars are speed limited to 130 mph; the 275s are limited to 112.

Compare the 2 engine torque curves, then let the "smaller" engine wind up faster with a higher final ratio...........
 

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Discussion Starter #16
Thanks for the explanation I didn’t know the gear ratios were also different. Another thing I’ve always wondered is either of the engines “more” or “less” likely to have the headbolt issues? I’m aware of the head bolt changes throughout the years but is there a pattern of more issues with either engine? Also is the olds aurora with the same basic engine more or less susceptible to the same issues?
 

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Vin Y or VIN 9 seems to make no difference in head bolt hole thread failures. Year groups do. Study the poll in Engines; Northstar, sticky threads, head gasket failures, poll.

1998 - 1999 the worst - had something to do with block casting metallurgy, I think.

https://www.cadillacforums.com/forums/northstar-engines-system-technical-discussion/122898-northstar-headgasket-cracked-block-bolt-failure.html

(Always study the stickies in any forum of interest - timeless info for all owners of the cars discussed in that forum.)
 

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Master of the Dark Art of Diagnostics
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Thanks for the explanation I didn’t know the gear ratios were also different. Another thing I’ve always wondered is either of the engines “more” or “less” likely to have the headbolt issues? I’m aware of the head bolt changes throughout the years but is there a pattern of more issues with either engine? Also is the olds aurora with the same basic engine more or less susceptible to the same issues?
==============================
Another thing I’ve always wondered is either of the engines “more” or “less” likely to have the headbolt issues?
NOPE -
the ONLY physical difference between a VIN-9 motor and a VIN-Y motor is the intake cams - that's it!
 

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Hey guys.. 2003 Seville SLS.. Always runs 1 click above halfway on the engine temp. Today in NJ it’s about 90.. I was sitting in traffic for maybe 15 minutes at idle with air on and I looked down and noticed that my temp had risen to about half way been halfway and the first bar. Traffic started moving again and within 50ft temp went back to normal.. by then I was home. Is this cause for concern? I’m tempted to go back out there and let it idle in the heat to see if I should be worried
Not to worry...just make sure your radiator is topped off using 50/50 antifreeze mix.
 

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This is a normal operation. During the hot months in traffic with a/c on they will run at somewhere near 205-224. ECT is pretty much just a temp-variable resistor so the readout on your car might be different, on some cars fans turn on at displayed temp 222, some at 224, some at 226. Don't worry too much over some degree difference. As long as the fans turn on slow at somewhere near 224 it's working normally. Plus you can't compare the "middle zone" with Deville because with their digital dash the middle zone is way wider than 188-215. Pretty sure their "middle" is 188-236.
 
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