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2011 CTS Coupe Premium
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Discussion Starter #1
Just got back from about 50 miles with the new thermostat/water pump and a little concerned about the ODB-II coolant temperature readings. Runs fine and stays on the dot below the 220 mark on the gauge. That said it was 92F when I left and 95F out when I got back. AC on whole time and every time I looked so was the fan.
Outbound 92F
At 70 mph cruise - 204-206F
At stoplight slowly rose to 212
Inbound 95F
At 70mph cruise 206-208F
At stop light 212-215F
Came down to cruise temp once moving indicating an air flow issue when stopped.

DIC showing 16.6 mpg for day. Coolant level same as at start.

To me this seems at least 15F high even at 95F outside and shouldn't rise that much when stopped. Ideas ?

Maybe tomorrow can get out the IR gun and check the hoses and radiator but a 180F thermostat (new Stant) should be full open well before any of these temps.
Is this normal for a DI 3.6 ?
 

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I'll make this the last bit of input I offer on it. That thermostat should be made in accordance with original equipment. It should function similar to the original equipment, cracking at 180F and full open at ~203F.

In the info label attached to it on Rockauto, it specifically states it gradually opens wider as the motor heats up, metering flow. It does not operate light switch fashion in the manner that the old style thermostats tended to.

It will probably run cooler if you turn the A/C off. Although it turns the fan on, it also draws the hot air from the condenser through the radiator. I didn't know how hot condensers got until I was burned by one while working on a car with the A/C on and fan temporarily unplugged.

If you have a known previous temp range under these conditions tell what it is. If you're going by feel, as long as the temps rise when stopped and drop when you start moving consistently, those temps are still in normal operating range.

Hopefully you will find some comfort in this, although it's the first gen;

 

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It sounds normal to me. I don't monitor the OBD coolant temp readings but the gauge typically stays on the first mark below 220 and I've seen it creep up until the fans kick on or speed up. I may have mentioned last winter that my temps ran 190-200f but that was winter in PA. In the summer, ~200-220f is normal for my car.

If the temps bother you enough I believe your best course of action is to swap in the larger radiator Joseph mentioned previously. You might also look into the possibility of lowering the fan-on temps by a few degrees with your tech2win. I previously shared your concerns to an extent but I'm over it. As long as my coolant stays below 220f I'm content.

With that kind of MPG I suggest that a manual cleaning of your intake valves should be of greater concern. After I replace my RF hub assembly and get my new inspection stickers, that is next on my list.
 

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My cars temp stay just below the 220 all day every day 110 or 115 ambient. and at 70 degrees too. runs just over 200 degrees.

I flush the outside of my radiators every year and take a brush to them every other year. yes they to collect trash.
 

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Discussion Starter #5
OK and thank you. Guess this is my first summer with the car but guess what bothers me the most is the ramping up when stopped even though the AC is on (and so is the fan).

As to the tech2win was told I need a $40 subscription for "something" to be able to set parameters and then can only do it once.

But first dot under 220 is apparently normal in the summer.

Even so the Specrum rad is now first on my list.
 

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Discussion Starter #6
Apparently the first dot under 220 can mean anything from 204F to 221F. Saw all today on OBD. 94F & went to Lakeland: mostly 204F @ 50 mph, 206F @ 70 mph. Higher when stopped. 118 miles 20.3 mpg indicated.

Bothers me that the temp jumps so much when stopped, my other cars may go up a few degrees but not that far. Wonder what the gauge logic is.
 

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Discussion Starter #11
I spent many hours as a GMI student in the back seat of instrumented cars running 250F for hours on end because it was easier (not better) to tune for a fixed temperature.

High temperatures is what caused both the Vega (not enough coolant) and Fiero (not enough oil) debacles - someone trying to cut costs. They also necessitate more frequent oil (both engine and transmission) changes.

For maximum life of everything under the hood (I suspect that is why the battery in my coupe is in the trunk) the "sweet spot" for a computer car is 180-190F. Further I target less than than 90F over the air temperature in hot weather. The AC also works better. My other cars have been modified to run there and have two I've had for over two decades. It works.

Now I could live with 200-205F if needful, it is the transients to 215-220F when stopped that bother me, they should not be happening with the AC (and fan) on unless something is causing it. Can't be a bad fan clutch so must be "something else". Eventually I will find/fix it. Since it is not very expensive, first I'll throw the larger radiator at it.
 

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I spent many hours as a GMI student in the back seat of instrumented cars running 250F for hours on end because it was easier (not better) to tune for a fixed temperature.

High temperatures is what caused both the Vega (not enough coolant) and Fiero (not enough oil) debacles - someone trying to cut costs. They also necessitate more frequent oil (both engine and transmission) changes.

For maximum life of everything under the hood (I suspect that is why the battery in my coupe is in the trunk) the "sweet spot" for a computer car is 180-190F. Further I target less than than 90F over the air temperature in hot weather. The AC also works better. My other cars have been modified to run there and have two I've had for over two decades. It works.

Now I could live with 200-205F if needful, it is the transients to 215-220F when stopped that bother me, they should not be happening with the AC (and fan) on unless something is causing it. Can't be a bad fan clutch so must be "something else". Eventually I will find/fix it. Since it is not very expensive, first I'll throw the larger radiator at it.
Tune for a fixed temp and add tables that compensate for changes from that point. The programming does that. The laws of physics prove that the hotter a motor runs up to a point, the more efficient it operates thermally. 250F will net better combustion efficiency than 190F as long as it can be safely sustained.

The Vega and Fiero debacles can equally and more reasonably be considered engineering failures, as they left the factory poorly equipped for heat and lubrication demands that were known to exist in advance.

Manufacturers are more interested in their profit margin & EPA demands than the best engine temp for longevity, so there's often much that can be improved on over stock.

I stated I wouldn't attempt to convince you any further on your concern with the temps you're seeing, so I will not comment on that aspect, but I do agree with your intent on achieving lower operating temps, because to us, longevity is priority.
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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Different car, different engine, different programming, but here's the later Seville 300 hp V8 temp gauge and its programming.

Temp gauge - my numbers.jpg


Heavily damped between 188 and 210 (thermostat opening/open range) - WHY? So that owners would not rush to the dealership because a gauge actually MOVED in response to changing operating conditions.

Using a ScanGauge-II and monitoring actual coolant temps my Northstar (warmed up and settled down) runs at ~195-200 degrees all day every day every month. Maine or Florida.

The Northstar uses 7.5 quarts of oil - for lubrication and cooling - oil is the only thing that cools all the reciprocating parts and chains. The oil runs at about 200 degrees for proper flow and to boil off any condensation moisture and blowby acid vapor for burning in the PCV system.

Perfectly normal to see engine coolant temps fluctuate due to changes in power demand, ambient temps, road speed, fan use, etc. One or two fans do not pull air through the entire radiator core - only part of it - UNLESS the fan(s) are encased in a complete surround shroud for the rear side of the radiator.
 

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Discussion Starter #14 (Edited)
Thank you, time for me to stop talking and get doing Just this is coffee time..

BTW "laws of physics prove that the hotter a motor runs up to a point, the more efficient it operates thermally" yes and that point is around a coolant temp of 150F. Beyond that it is the area under the PV curve (Pressure Volume and I promised no math but it is hard...).

Now the cyl head of the 3.6 is about as modern as you can get, a 4 valve pent roof (better than a hemi) with center plug - anyone index their plugs ? Before the slant plug chevvy we used to point the gap at the exhaust valve - but I am not supposed to reminisce - sorry but the way I think everything at once - anyone see Cassandra on "The Librarians" - oops doing it again

Ps - I was a GMI student & a gearhead (unusual) at GMI 1970-74 so saw a lot about the Vega. It was just a fact that you had to keep the walls of the cyl relatively cool, Overheat A Lot and the silicon carbide (wear resistance)particles would separate from the walls and would be kind like pouring sand down the carb. Starnge thing, the earlier ZL-1 aluminum 427 never was chided & was the first to use that process. Of course it was a three grand option in a three grand car. My cars all had AC so real radiators. GTs were great cars even in Texas.

pps thanks Sub and "runs at ~195-200 degrees all day every day every month" would not bother me at all. It is the 215-221 I saw yesterday while idling with the AC on that bother me. BTW my next car will probably be an XLR which has a NorthStar...
 

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Plug indexing - memories. Chevy 327s. I still have a box of various thickness index washers. Gap toward the intake valve ????

The Northstar uses a 4-valve pent-roof "semi-hemi" configuration.

northstarr4.jpg
 

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-Administrator- 2002.5 F55 STS 2014 FWD Explorer
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Hey, Padgett -

Hickok tube testers - I have nine of them. 539 A, B, C, TV-7, TV-10, others. Been a tubeaholic since 1952. Got thousands of NOS tubes. Scored a two hundred box of NOS Amperex Holland Bugle Boy 12AU7s a few years ago - medical equipment company, bulk pack, $25 for the LOT. Remember Fair Radio?

Eat your heart out ..... my workhorse. A mint 539B. Always use a plate mA meter for power tubes.

H539b.jpg
 

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Discussion Starter #17 (Edited)
Hoo boy. You've been looking at my web site. Personally I like the TV2 better.

Also agree but they are just calling it a "semi-hemi" for marketing, is really a "pent roof" since the intake valve stems have to be on a common plane and so do the exhaust valves.

Gm has had 4 valve DOHC engines back to 1987 (quad-4) - not counting the Cosworth-Vega. Funny thing is that a number of Mercedes engines copied GM designs (balance shaft, offset crank...)

Back when I was a student prepared a paper on lozenge shape valves with dual stems (unleaded gas does not need valve rotators) to maximise valve area. Never went anywhere. Neither did the throttle position limiter to limit detonation (though suspect the new fly-by-wire systems do that automagically)

Got into it with a major cam manufacturer (initials BC) who was promoting ded cams which also killed power. My design allowed an engine to run aggressive cams and stay right under detonation but in 1973 the technology was not there.

Boy we could have fun in a bar (or a garage). Mine probably qualifies for an Archaeological dig by now, just came across a can of Harley-Davidson Pre-lux 60wt oil. Prolly belongs in banter but what the hay.

ps spent a lot of time in my yout in Easton (the only occupied state) sailing Penguins before I moved up to Lightnings.

Oh, no you pointed the gap at the exhaust valve - hottest part of the cyl - to reduce detonation.
 

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Just got back from about 50 miles with the new thermostat/water pump and a little concerned about the ODB-II coolant temperature readings. Runs fine and stays on the dot below the 220 mark on the gauge. That said it was 92F when I left and 95F out when I got back. AC on whole time and every time I looked so was the fan.
Outbound 92F
At 70 mph cruise - 204-206F
At stoplight slowly rose to 212
Inbound 95F
At 70mph cruise 206-208F
At stop light 212-215F
Came down to cruise temp once moving indicating an air flow issue when stopped.

DIC showing 16.6 mpg for day. Coolant level same as at start.

To me this seems at least 15F high even at 95F outside and shouldn't rise that much when stopped. Ideas ?

Maybe tomorrow can get out the IR gun and check the hoses and radiator but a 180F thermostat (new Stant) should be full open well before any of these temps.
Is this normal for a DI 3.6 ?
I own the same car as you....with 110,000 miles. I bought it new. Original stat. No issues so far.
I was playing around under the hood recently and removed the long plastic trim piece that runs along the front of the engine compartment (just adjacent to the front grille). This exposed a full view of the radiator, which was COVERED with crap, bugs etc. from 9 years of much long-distance driving. I hosed it all off and I "think" my temp needle now rests about one "mark" lower than it used to.

In the pic below, you'll see the needle sitting just slightly below the notch below the 105 C mark. If each notch up to that point represents approx. 11C, then this looks to me like approx. 93C or 199F. This is fully warmed up, air on, at idle. The temp does not fluctuate once operating temp is reached.

I know....this is wildly unscientific
IMG_0159.jpg


......but just saying'......looks like you've done a ton of analysis.....but make sure your rad is clean on the outside.
 

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...
BTW "laws of physics prove that the hotter a motor runs up to a point, the more efficient it operates thermally" yes and that point is around a coolant temp of 150F. Beyond that it is the area under the PV curve (Pressure Volume and I promised no math but it is hard...).
That's math I'd have to see. Regarding expansion of gasses, more heat from the combustion process will be lost to the surrounding cooler walls bathed in 150F coolant, than at higher capable temps of 200+, where more of the hot gasses will stay expanded in the cylinder to do work against the piston. It's the temp differential that promotes heat exchange of hotter to colder. The exchange rate however, is important to illicit how much of the usable temp range is worth the effort.

Now I'm speaking only of the simplified combustion chamber process, meaning all else the same, not hotter running engine coupled with hotter inlet air temps, as the two are inversely proportional. There are other factors of operating conditions of course, that could be brought in to increasingly confound the fundamental theory, but you seemed to have finally started to get comfortable with the temps you're seeing and I don't want to get you started on something else.

I was told years ago that NASCAR ran high engine temps (~290F) for fuel efficiency, but that's only a small part of the reason.

Some modern day super cars BMW M3 models for example use 10W60 motor oil, can you believe it.
 

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Discussion Starter #20 (Edited)
And just when you thought it was safe... I am continually experimenting with different things. Went to get shorn and pick up some things at the mart at the wall, came home and was sitting in the driveway with AC on. 93F. Temp was at 215 and slowly rising. Applied throttle from 600 rpm idle to 1400 just sitting there and temp dropped quickly to 206. It would appear that the issue is one of flow and not capacity. Would also explain why the rad hose has felt cooler than I would expect (part of reason for changed thermostat). Suspect all I may need to do is to raise the idle to 900 rpm (have done that on computer cars before to increase AC output at stoplights. Might be why I've never seen this before.

BTW 10w-60 does sound silly, almost needs to increase viscosity as it gets hotter (would need to look up the SAE standard). Back in the day we used increased weights and motor honey (STP) to increase flow in a worn engine or to save an engine that was starving in corners. Would doubt that any engine is running coolant at 290F, even for an oil temp that is high but then the engine gets rebuilt every race.

ps your cluster looks the same as mine, just different numbers: 105C = 221 F
 
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