Have my new engine in with about 500 miles on it. It runs around 205° most of the time.

However, once in awhile I will see it climb up to 220 and then drop back down. Does not happen all the time, but it does just seem a little odd...and I am in no mood to damage this new engine!

 

I just got my 2011 LT about two months ago, so I'm still learning about what to expect. It's been cold here until this week, when I've been seeing the coolant temp fluctuate from its normal 180°-183° window up to as high as 214°. I expect it to run a little warmer, but I've never had a car with a digital readout before, just the needle (which in this case has never read above "middle").

Is that bad?

 

I would start by checking the coolannt level, or just put a splash of dex cool in....not the green stuff!

220 is a bit high but shouldnt hurt anything...

 

New or freshly rebuilt engines have internal clearances that are a bit "tight", so they can run a little warmer until they have broken in.

Keep a eye on your coolant level, and check the oil daily, you should see the engine running cooler as it accumulates miles.

 

I add a bottle of water wetter once a year to my 07......at 76,000 miles i run betwwen 189 and 192......the highest i have seen it go up was 210 at highway speeds (85 - 90) on a very hot south florida day (98 degrees).

 

If the A/C is not running the radiator fan comes on at about 220F then goes off at about 186F. If the A/C is on the fan always runs. In other words, you are running "normal" temps. But make sure you have the right type and amount of coolant don't trust other peoples judgement about fullness, CHECK IT YOURSELF! Open the pressure cap when cold, the coolant should fill the hose.

 

183F is pretty low. The t-stat should be 190F, sounds like you have a 180F. Unless you have different specs, anyway.

 

My ss runs around 200, then when idlin or traffic 220. I programmed the fan to come on at 210. Try adding water wetter. Once i added that to my 40dex 60water i am now running around 195 and 210 in traffic. Idling still gets to 217 but still below 230:)
Also make sure u have no air in the lines. My bleeding process was a pain...

 

What's supposed to happen at the T-stat set point?

 

I don't think so. These cars are just plan weird on engine temperatures. I get anything from 183 to 220, depending on the ambient and circumstances.......and that has occurred since it was new........with the OEM thermostat STILL.

For example, I can leave my house and drive approximately 3-4 miles and enter the freeway. I'll drive for about 20 minutes, at freeway speeds of 65-75 MPH, with the temperature at 183-185 (I always drive with the DIC indicating engine temp.).