I have an old cro-moly MTB frame that I have built into a beater/kid-trailer towing bike, got the frame for $10 used. It came with a Shimano cartridge BB installed. The BB is getting pretty rough and crunchy. After using most of a can of penetrating fluid and a 4' breaker bar, I've come to the conclusion that this BB is staying in there. Yes, I know the DS is left threaded. I can't budge either cup. I've tried giving the breaker bar a few raps, I've tried giving it a pull in the tightening direction before trying to loosen it. I've been applying the penetrant for about a week now (not WD-40), both to the outside and through the cable guide screw hole.
Has any-one ever attempted to force new grease into a sealed BB while it was still installed? How would you go about it?
If I can't service this, then I guess the frame is toast. I don't mind scrapping it in principle, but there's not many suitably cheap replacements available around here in my size.