I haven't read Greg's posting in the Diesel section but, I didn't have a problem with opening the block drain. It is located on the passenger side of the block. I don't remember what size it is. Removing this plug allows for all the coolant to be drained. With this plug removed and the radiator plug closed, I ran some clear water through the expansion tank and watched the water coming out of the block drain. Once it ran clear, I put the drain plug back.
1994 MB E320 Coupe (199,500 mi)
1992 MB 190E 2.6 (173,000 mi)
1983 Porsche 911SC (148,000 mi)
2004 Volvo V70 2.5T (198,000 mi)
President of CT/Westchester Section