This is what I've always done. Run a sheet metal screw with a beveled hex head in as far as it will go and when it start to turn the plug. Then, close the jaws of an adjustable wrench around it toward the engine. Then start to lever stuff in there and try to lever it out as you turn it with a 1/4" drive ratchet with a socket on the head of the machine screw, take your time. It has never failed me on many different makes and models. It will squeak on the carbon as you remove it. Run a reamer in there afterward.

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1987 300SDL #1, 1987 300SDL #2, 1980 240D, 1982 300SD, 1994 S350, 1990 350SDL, 1991 350SD, 1985 300D, 2005 E320CDI

Gone, but not forgotten: 1981 300SD, 1982 300SD, 1987 300SDL, 1983 300TD, 1980 300CD, 1981 300SD #2, 1987 300D, 1987 300TDT, 1980 300D