I may take a look under mine this weekend, dont know how to tell if it has, only getting the #s. I can tell someone has had an impact on my crank bolt. Couple that along with a new rad. and some crusted black goo on the backside of my old water pump impeller tells me this thing may have been apart before....Or its on borrowed time, one or the other. Why else would someone mess with the crank bolt?
Im guessing if it was carbon or oil the problem was fixed (or someone added a lot of sealer in a can which never really works) or it would be acting real funny by now.