How hot before boiling over?

[1BAD68]

I've determined that my temp gauge is 25 degrees off and my engine runs about 180 degrees even though the gauge reads higher.
When I shut it off and wait a minute and then turn the key to the run position, the temp gauge reads 230 which is the highest I've ever seen it but actually its about 205 degrees according to my infrared meter.
I'm just wondering at what temp will it start overheating?

[Tilar]

Depends on the coolant mixture.

[John_Kunkel]

Boiling point depends on the pressure cap, more psi means higher boiling point. It's perfectly normal for the coolant temperature to rise significantly after shutoff and heat soak, I've seen 240 on mechanical gauges when the running temperature was under 200.

"Overheating" is a relative term, means different things to different people. I would say an engine is overheating when there's danger of structural damage. Type of oil also has to be factored in, synthetics will take a lot more heat than conventional.

[Brass]

I have really been wondering about this also.  Now that it is warmer, the temp just creeps higher and higher and higher.  Driving around town has become a "pins and needles" experience.  Especially in Seattle stop and go traffic.  It isn't unusual for the gauge to creep up around 230 or so, and is always pegged after shut off.  I think my gauge must be inaccurate too... but the cab does get a little toasty.  An infrared meter sounds like a good idea.

[elacruze]

Broadly speaking, you can expect every PSI in the cooling system to raise the boiling point by +3*F.

Glycol has a higher boiling point, and some will argue that this changes the mixture boiling point; it may change the 'boil-over' point, where the entire system is overcome, but local gassification will happen to the water whether the glycol boils or not.

http://www.evanscooling.com/assets/pdfs/HD-Trucking-article-June-09.pdf

http://www.evanscooling.com/

[John_Kunkel]

I have a car that is running at a higher temp than I like and the car's layout prevents increasing the cooling system without major surgery.

I have looked into the Evans coolant and still might go that way, they make it clear that ALL of the existing collant must be removed for best results and then there's the oil temp problem that comes with increased coolant temps. Just can't win.