Well, it happened again. So I gathered the housing cover nipple is broken off, and that is what is inside the hose from the radiator. I did search on the subject and found that the plastic covers are to be replaced with a metal one so my inkling that the plastic "insert" inside the hose was really a broken off part of the thermostat housing nipple seems confirmed. So, the replacement metal part will be ordered tomorrow and the hose and thermostat housing cover will be replaced. I think I will flush out the coolant system too as it seemed kind of grimy, a brownish color, while the new stuff I was putting in was the MB fluid and it was nice and clear. The previous owner had the head gasket replaced and I suspect he did not have the coolant system flushed out. The biggest issue was the wife was out driving it when it happened the last time and I had to go retrieve the car. Not good for the image.....Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)