I have removed my block drain plug on my 240D and two Jeep Cherokees. I like to do this to get the crud out of there. But as stated before, a 15 to 30 year thread that is rusted in is a PIA to get out. I don't know about cracking the block. I would spray with PB Rust blaster or Kroil. Might aplly some heat. Not read hot, but a color change of blue, so 400F. A propane torch might get it.