MF461 coolant drain plug locations?

[sawtooth]

I'm trying to change the coolant in my tractor. I have located the radiator drain but not engine block. Can any one help me locate it please?

 

[sawtooth]

Here are a couple pics. In the first one I thought it was the tiny black colored star head just to right of sensor. The sensor is one above white Label with the silver nut around it. But i unscrewed star head what came out looked to be a ticker oily substance vs coolant. Also what is that sensor? Coolant temp sensor?

 

[sawtooth]

Anyone?