Lots of threads and discussion of this topic in the dim, distant past.
Basically as I read it
200-220 = normal
240 = watch it, not desirable long term
260 = shut it down and let it cool off
I got excited when the temps on my LS3 swap were running 230 - 240 and was told that the danger temp is 260.
The synthetic oil is good well into the high end of 200s
Modern motors "like to run hot". Wear is reduced when you run 200 and up. pollutants are reduced at higher temps. Modern engine tunes like the motor to run 200 and up, limited by break down of the oil.
My 2.0 ran 200 normally, 205 if the heater was on, 215 if the A/C was on at slow speed while climbing.
My 2007 GXP runs at 199-201, but with occasional spikes to 207 and lows to 195. It was constantly at 199-201 the first five years until I had my coolant changed by the dealer last January, after that it was 189-216! I did the hand method to remove the air from the system and got to 195-205. Then had it up on jacks and found a couple handfuls of leaves in front of the radiator. Now I'm back to 199-201.
Actually, the hotter the engine runs the more efficient it is in converting the chemical energy to mechanical energy. The downside is that it is hard on some of the engine components the hotter you get, but that is where modern synthetic engine oil really helps out with the higher temps being ran in newer engines. There were some experiments by Fedex back in the day with running engine blankets on their engines to keep the temps as high as possible to increase fuel economy on their fleet. I think this is also the reason that a lot of the newer cars do not have a temp gauge in them at all, otherwise people would be worried. To give you an example, the MINI's that we work with typically run around 220 and the Sonic's run in the 210-220 range all of the time. Like I said, the hotter they can run the engine, the more efficiency they get and since every MPG matters we should keep seeing OE's push those operating temps as high as they can get away with and keep longevity of the engine. Both of the cars I mentioned, the MINI and the Sonic, also have electronically controlled thermostats now also which allows the ECM's to do really neat things like run the engine hotter during cruise conditions, but lower the temps under full load, varying RPM's, etc.
Like everyone said though, I am not worried until I see over 240 on a GXP/Redline. Usually though we see these cars cruise around 195-210 depending on load and ambient conditions.
Thanks for the perspective, Dave. We really should sticky a 'temperature' thread.
I have an offshoot question regarding the Tstat and hvac system that I never bothered to ask but since we're all here and OP's care is safe, I'll just tack-on.
My temps (LE5) went from the standard ~190 during operation to ~210 after I added the water-cooled turbo. Sitting idle, temps will creep to ~225-230 and especially when I have the temp set to any variation of heat or if its using the compressor. The fans do come on and know I should take a look at their settings in HP Tuners (my old laptop broke that I used iniitally) and the temps will drop back down if I adjust the temp to cold. I also replaced the tstat at the same time (due to occasional ---F readings which turned out to be the commonly broken inner seal).
All that said, could the almost-instant temperature change be because of the coolant line I tapped for the turbo? Adjusting the temp flows more the turbo's (hotter) coolant past a sensor or something? Back in the day, I thought (possible misconception as well) turning _on_ the heat helped lower temperatures. Obviously all this changes with the compromised coolant system (and the added additional radiant heat) but it was something that I've wondered.
I have a 2007 2.4 solstice. Today I was driving and it’s the first time I notice that the temp was 230-240. The heat outside was a touch over 100 and very humid and with the air on. Should I be worried?
Seems high my fan on an 07 kicks on at 214 and cools it down to around 185 /190 . When was the last time the coolant was changed GM recommends every 5 years . Another issue on an NA is the thermostat I had to replace mine at 28000 miles and I service my car per GM recommendations .To be on the safe side I'd do a coolant change ,replace the thermostat ,not hard to do ,and check your hoses .
Some simple things to check. The radiator draws air from under the nose of the car. put the car up on stands and inspect the front of the radiator for debris. Over time the radiator can be partially blocked by grass, paper, all kinds of junk. Even bugs can add up over time. Alternatively, get a hose and flush the radiator from the back side to see what comes out. Not high pressure but good volume of water can float debris out of the radiator fins and onto the ground under the car.
As has been stated many times, 190 to 210 is "normal nominal" temp. On a hot day as you describe and with the AC turned on, 220 to 225 is not unusual. But it should drop if you turn the AC off or go down hill for a few minutes. If its going above 230 and staying there, its not damaging anything but its on the way to a bad place. 240 is generally considered an upper limit for the oil. and it will shut down if the ECM thinks its "over temperature"
Depending on how many miles you have there are other failure modes that are low probability but possible.
Work out radiator hoses tend to fail from the inside out and can be sloughing off their guts into the radiator blocking it. This was a relatively comment occurence in the 50s and 60s for older cars.
The thermostat may be failing and not fully opening. Rare but possible.
Try cleaning out the radiator first and check all the hoses.
The air conditioning will shut off automatically to reduce load on the engine and radiator if an overheat condition is predicted by the engine controller. If your a/c is still blowing cool air, you are in a normal temperature range and not at risk.