Funny- I am having the same issue (on almost the same day!) but on the other side of the US. I tried a hammer - now that I read this post I will try a little harder.

One other piece to add - I changed coolant in my 84 300 sd to Zerex a few weeks ago. Drove it about 200 miles then noticed a leak coming from below the water pump (coincidence??). When I released the bolts I had a lot of coolant come out, but it looks green (the older stuff) despite the fact that I thought I had flushed it almost completely by draining, refilling, running, draining, refilling, etc. about a dozen times. Any ideas on why I had old coolant inside?

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dannyf
1984 Mercedes 300 SD 214 K miles. Runs on WVO ~ 22 mpg over 8 K on WVO
1997 VW Passat TDI 156 K miles. Uses biodiesel and diesel. ~ 41 mpg
1996 Mercury Villager gasser. ~ 20 mpg