Sorry to hear about your troubles, especially knowing that you only recently acquired this vehicle (relatively) - that is a PIA. At least you are well connected on this forum and are equipped with the knowledge of what needs to be done to fix the problem. One thing I noted from reading your story was that you mentioned the coolant was orange, which the PO had swapped in for the OEM coolant previously. I know one of the only approved coolants other than OEM readily available in the US is Zerex G-05, which is a yellowish hue. Doesn't sound like the wrong coolant would have caused this problem anyways, but any chance the wrong coolant is in there?