I am at 71k miles. Try climbing a 6% grade at 70mph and 110f outside. You will hit 230f on the coolant if the climb is long enough. As said, GM sets the overtemp warning around 250f. That is the warning point because you are close to the coolant boiling (around 265f depending on mix and pressure.) 250f is not impending doom. Now if I saw 240f, I would back out of it to get it down but again only becuase I don't know where it will stop and I don't want to blow the coolant out. If that happens all bets are off. I trust a modern engine at 230+ over and old iron engine. Better metals and tolerances. But wouldn't push my luck for sure.

I thought there might be well known head gasket or sealing weakness. I can't find any evidence there is a chronic issue with coolants over 230f for the LNF.

 

The LNF had porosity issues, and head gasket problems mostly due to overheating.

 

I don't take limp home mode as a warning.

Keep testing your theory for us.

 

And if you keep on going with it there is another warning feature where the system near instantaneously purges pressure and gets rid of some coolant all over your engine bay as an added precaution. The hoses burst to relieve pressure. XD in all seriousness. 250 is way too hot. 230 is too hot. They don't make engines out of some space age material. It's just aluminum. 250 is bad.besides that is the coolant temp not necessarily engine temp. The car even tries to tell you that by intentionally misfiring because it realizes the coolant ain't coolin 😎 . Please, future forum members are going to run into misinformation like this and kill of what remains of our hhrs.

 

Well it's time to close this thread down - it ended up competing pretty closely to the one about drilling a 1/8" (not a 1/4 or 1/16") hole in the thermostat.

Anyways, it has been discussed, points made from both sides. Obviously there will not be a general agreement.