[911monty]

Wow. Good job hanging in there! What a mystery. To answer your question regarding the cooling system hoses, well this is where a bunch of engineers got together and decided to redesign the wheel. So unlike american iron, the thermostat on these engines controls the coolant as it returns from the radiators not to the radiators. So it should be cooler than the coolant from the engine block which is the hot side to the radiators. Confused? Yeah they also designed the IMSB. I think their reason was so that coolant is always circulating through the oil cooler.

The coolant leaking from the overflow is still a question, unbelievable. The last thing I can suggest is this. In your pictures of the hoses on the coolant tank the one with no clamp is the drain hose. Can you remove it preferably at the manifold connection so you can put it in a container? Then start your engine and observe for leak? It has to have a source. I do not believe in magic.