where does this plug go?

I was working on my VX, when i noticed that a connecter had come off. I put it back where i thought it came from, i just want to know what it was, so i know i didnt mess anything up. If your looking at the engine, it is behind the highest pulley. the back of it is a plug, while the front of it is a threaded insert. It looks like a sensor or something. from the "sensor", it goes to the radiator hose and into the radiator. Sorry i couldnt be more descriptive. Anyone know what this is?

Brian

it goes in the back of your head...it runs the auto machine gun, missles, rockets, and all of the other SPECIAL functions!!!!
just plug it back in and it will be alright.