Stuck Freeze Plug
 

'91 300e 2.6

Well I got the govenor and drive gears all replaced, thanks to all who helped on that. While under the car, a constant drip directed me to a leaking freeze plug. The thing has a hole in it. I have a replacement, but the problem is that I just can't get it to budge. Took to an shop and they weren't able as well. Any suggestions on how to free this thing. I've doused it with PB Buster and Liquid Wrench. So far, nothing.

I should clarify, this is the plug on the rear passenger side of the engine. The one that screws out. Thank you.

Gave up and took it to the shop
 

Finally just gave up after trying everything I could and had it towed to the shop. They went ahead and welded on a socket and took it right off. The indie is a good one here on the Island and really fair. He said that I never would of gotten it off without heat and welding. Only sad thing is, its the first time I've ever had to have someone else do a repair on this car. Something of a pride thing I guess.

If there was enough room to weld, couldn't you have cut it out with a chisel?

How would the chisel have removed all of the plug? It could shear the top part off, but how would it have helped with the threaded postion that was stuck?

I'm not familiar with this particular plug, but I was thinking along the lines of poking a hole or cutting a short slot in it and prying it, distorting the shape until enough threads pull away or loosen that it can be popped out or easily unscrewed.

I'd imagined it might be similar in size, shape and thickness to a standard engine block freeze plug (only threaded in with perhaps a stamped hex head in the center).
But if it's smaller or thick walled I guess this wouldn't be practical. A hardening sealer is used many times on freeze plugs, if it was used on a threaded plug it certainly would be pretty hard to get out.