Unless the plugs are totally dead there is something else you can try.

Run 12V directly to one of the plugs, and let it heat-up for at least 2 Minute. Try removing it immediately after. If you get a hefty spark when you connect the 12 volts, that's good. You know that that plug still has some life in it. If not, the plug is dead.

If that does not work, an UNEXPLORED idea, is to connect 24V (2 * 12V Batteries in Series) directly to the plug, If the heating element is still working, even a bit, the super heated plug may than be more agreeable to come out.

At worst (actually at best), you may cause the plug to disintegrate, with its pieces falling into the pre-chamber. If that happens, the plug will than easily come out. The pieces can later be extracted by removing the pre-chamber. Certainly easier, and cheaper, than removing the head.

As I said, I have not heard of anyone trying this, but I don't see a downside to it. It may just work. Can someone else comment?

Phil

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'95 E300 Diesel, 264,000 Miles. [Sold it]