I agree with Peter. If things are dry on top and as wet on the bottom as the photos show, it's either a lower hose connection or water pump. I'd bet on the pump. The loosened cap suggested earlier is to prevent pressure build up - something you don't need under these circumstances.

The green coolant should be changed, but unless it was mixed disproportionately..ie 70% coolant; 30% water, it had nothing to do with causing any sort of overheating. Even if it was mixed this thick, it didn't take out the pump.

Get a new one.

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"