I own a 1992 z28 Heritage Edition 305. The car shows that it’s getting way too hot before the fans kick on which may be my temp sensor. I haven’t fully ruled that out yet. But when the car gets hot and the fan does finally kick on, if i turn the car off, the fans turn off. Then the car overheats. I did find a plug in on the radiator. looks like a sensor connector of some sort. Is there anyone that knows what this is? And anyone know why the fans are doing this? Any advice or info is greatly appreciated!

 

That is a coolant level sensor, on the radiator.
The fans are doing that (turning off) b/c that is how the car is designed. When you shut the ignition off, power is cut to the relays that power the fans...fans turn off.

HOWEVER....
Continuing the running of the fans after the car is off, wouldn't prevent or have an impact on this at all. What is happening there is that your cooling system is not working efficiently when it's running so it's already "too hot"; maybe not over heating, but hotter than it should be. In addition, your oil is too hot....hotter than the coolant. You shot it off, heat from the oil (and other hotter places of the block/heads) transfers into the cooling system, it boils and/or pushes out of the cap into the overflow tank.

What do you need to do? Diagnose and repair and improve the functioning of your cooling system, likely by cleaning out the space between your condenser and front-of-radiator, or possibly replacing the radiator if you haven't done good cooling system maintenance....which most people do not.