Hi all -
I have a 76 F250 with the 360 in it.

Yesterday I replaced the radiator and am in the process of flushing out the old coolant. Last night while doing this in the dark I did not add enough water to the radiator for the first flush. The gauge was reading full hot and I shut it down. This morning I drained all of that fluid and filled her up with water to flush it again, but the temp gauge will not come off of cold.

The gauge was working last night, read hot, and this morning after idling it for 20 minutes with the new radiator full of water, it still reads the same as if it is not running.

I am going to dump the water and most likely install a new thermostat, but is there an issue here I am missing?

Does anyone recommend a good thermostat also?

 

Welcome to the site, is there a stat in the engine now? If not the engine will not warm up enough in 20 mins. to read on the gauge. I run a 180 degree stat in my 390 and a 190 in the 460 engines in my Bronco and the 76 F250. A good stat from NAPA would be good

 

Yes there was a 195 thermostat in it already. Last night it must have just heated up so much quicker because I didn't have enough fluid in the radiator. I just installed the new thermostat and am going to flush again and see if the gauge reads anything or not. Ill try letting it idle for around 25 minutes.

 

Don't rely on the original electric gauge - if that's what you're using. It's meant more as a go, no-go warning indicator and they do drift over time. To properly diagnose engine temperature issues, a mechanical gauge is much more reliable.

Also, are you sure the thermostat was oriented the correct direction?

 

Don't forget to open the heater valve so you completely flush the old stuff outta there. Doing so also helps to circulate/vent trapped air. But you already knew that, right? Personally, I also drill a small 1/8-inch hole on the T-stat to vent any air trapped in the block.

2x on relying on the stock gauge. MotoRad makes a T-stat that fails in the open position. That might be worth looking into... MotoRad - Fail Safe® Thermostat

 

X2 I do this too.

And like others have said get an aftermarket gauge to show what the water temp actually is.