What is normal operating temp for 3FE?

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Feb 19, 2010
Largo, FL
I'm asking because my stock guage has been acting up lately, so I installed a mechanical temp gauge and I'm trying to dial in my e-fans to the correct temp. I currently have them set to turn on @ 185 and turn off @ 180.

Thanks for the help.
will the stock thermostate is a 195 degree
so that would say 195, but you can have 185 degree,
thermostate so it all depends on which thermostate you have.
I have an aftermarket Nordskog temp gauge with the sender in the t-stat housing below the t-stat (opposite the stock sender). I have a new OEM t-stat. I have a new aftermarket 4 row radiator. I run dual SPAL 11" fans in a custom shroud with a Delta Current Control variable speed controller. I have it set to come on right around 200. This setup maintains a temp range of 198-203.

I tried running a 185 t-stat but after comparing it to OEM I went back to OEM. The opening is physically larger in the OEM t-stat. I believe that the 185 version I was running was restricting flow. Wasn't a problem unless it was over 100 and I was fully loaded down pulling a grade. The OEM t-stat also seems more sensitive (maintains a smaller range of temp fluctuation with the same fan/controller setup)? May just be perception and not reality though.
I have a thermocouple attached on the outside casting of the engine and it gets up to around 185 on the streets and around 200 on grades. On hot days and pushing it I have seen over 200.
Thanks for the info. I have it set to turn the fans on @ 200 and off @ 190. It seems to be working well cruising around town. I'll have to take it on a little road trip this weekend and see how it does on the interstate.
Another question, What is too hot?
I know the boiling point of antifreeze/water depends on the system pressure...but assuming stock cap in good cond. and 50/50 mix, what is the max safe temp?
FSM says 88C / 191F. Is that the *ideal* temperature for these engines, or just what the specced for US trucks due to emissions? Did global market trucks have different thermostats? It sounds like the 2F came with a couple different thermostats depending on the year.

I've heard that there's no reason (maybe other than hotter heater output or emissions) to have thermostats hotter than a certain temperature.

This comes to mind: Race Thermostat - BDK - https://bdkraceeng.co.uk/tc/products.php?276

Also curious about this for the 1FZ, and if anyone deliberately fits a cooler thermostat.

Edit: More info: 170° PERFORMANCE THERMOSTATS by Reische Performance Products - https://www.reischeperformance.com/WhyLowTemp.html

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