# How hot is too hot?



## Daved_XB (Sep 22, 2016)

Hi guy’s, 

My 69 GTO up till now only had the idiot warning lights in the dash so I’ve never know how hot the engine runs, I just know that the temp light comes on when I turn the key & goes out once the engine is running so all seems fine there. I fitted a set of Autometer gauges the other day as I want to see what was actually going on.










I noticed that there was a “spare” tapped plug on the intake manifold so that I was able to keep the factory idiot light set up & add in a 2nd sensor for the new gauge.










Now that I have the gauge in I’ve noticed that the car seems to run at about 210F & that’s a little hotter than expected it to be to be honest. 

Is 210F too hot? The car doesn’t behave or smell likes its overheating… I’ve no idea what thermostat is installed in the 400, is this something I should be worried about?

Dave


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## PontiacJim (Dec 29, 2012)

First, could be the gauge as some are more accurate than others, and it does make a difference where the sending unit is placed. Some guys like to use an infra-red laser temp gun which can be bought cheap enough at your local parts store and check a few places on the engine, radiator, hoses, etc. to get a better reading of the engine overall. You can also see what the temp is at the gun as compared to your temp gauge at the dash and see if there is any difference.

210 is not scary. You may have a 195 thermostat which would make it run a little hotter like you are showing. A 180 may make it run a little cooler, but there are many other factors which have been covered on the forum if you do a search.

You will find that there are differing views as to what is a good temp or what is too hot. Personally, I like to shoot for 180 while steady cruising, but that is my choice. It will go up in stop/go traffic or hot days, but that might only be 200. So if it were to go higher in stop/go traffic on a hot day, then I would be a little concerned and look for things to do to get the temp down, so that is the real test for your car. :thumbsup:


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## geeteeohguy (Feb 2, 2008)

210 is not too hot. Not even a concern. 230 is too hot. That's when the light will come on. Optimum operating temps for these cars is 180-210. Most of us gearheads like to see the temps at the 180-195 range, but in reality, 210-215 is perfectly fine and won't hurt a thing. New cars run at 220-240.


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## Daved_XB (Sep 22, 2016)

Thanks guys... get info, think I'll swap out the thermostat for a 180 & see if that brings it just below the 200 mark.

Dave


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## dimitri (Feb 13, 2009)

I would also make sure you have the correct working radiator cap. 210 is a good temperature.


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## 1968gto421 (Mar 28, 2014)

I like Jim's 180*-200* temps. Reason is I've seen the hotter the engine, the more prone to pinging/detonation. My 2 cents.


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## geeteeohguy (Feb 2, 2008)

I agree with that, for sure. An engine running 180-- 190 is a lot less likely to detonate than one running 215.


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