You got a bad or the wrong sender, should look like this:
https://m.media-amazon.com/images/I/61sFvK2ShoS.jpg
Replace it
If it has a Cone shaped tip its a 5v sensor not a SENDER:
https://i5.walmartimages.com/asr/88....jpeg?odnHeight=612&odnWidth=612&odnBg=FFFFFF
When engine is cold take one heater hose off at the firewall, doesn't matter which one
Refill radiator until coolant is coming out of firewall AND hose
Put hose back on
ALL the air is out
The heater is on the engine side of the Thermostat, rad cap is on the radiator side
When engine is cold thermostat is closed
So when you refill cooling system air gets trapped in the engine/heads behind thermostat
Heater hose is at rad cap level, so with a hose removed coolant can push the air out as you refill via radiator cap opening
Easy peasy lemon squeezy