[SRR]

Originally Posted by Formulajones

They all pretty much start to open before the rated temp. I've bench tested a bunch of them when I was experimenting with them years ago. The rated temp on these things is just a "range" there is nothing accurate about them.

A 180 generally will start to crack open around 175 to 177 degrees and they aren't fully open until 182-183 or so.

In most cases, if you have a car with a good cooling system capable of doing the job the engine will stay right in that temp range on hot days. On the really cold days you'll see the engine running around 175 degrees or just below the 180 rated thermostat setting because when these things start to crack open, that's enough flow to keep things cool with ambient temps in the 20's, and even ambient temps in the 50's, which is exactly why the poster in post #17 is seeing 175 degrees on cold days with a 180 stat. But by no means should you see the temps running 120 like the OP. That means the thermostat is stuck open in some way.

Think of thermostat ratings as being the coldest temp the engine will run, but it doesn't mean it will stay there on hot days if you don't have a cooling system capable of doing the job.

I've done the same with a heat gun and an infrared thermometer. I put a 160 in my 95 Jeep and on cool days it runs around that temp. and on warmer days depending on traffic it will hit 210.

[65sport]

What is your radiator fan setup ? But I agree thermostat first.

[amcmike]

1. Replace your thermostat with one that functions properly.
2. Consider a clutch fan or electric fan for faster warm-up.

The electric fan is a little better as not only will it only come on as needed, but it will provide full cooling capability independent of engine rpm. It will also free up a few ponies. You might need to upgrade the alternator.