I was replacing the water pump on my truck cuz it had been leaking...I went to tighten a bolt down and I don't know what happened but a bolt broke off down around the threads(and it was the last bolt too

), so I got everything torn down so that the broken bolt is sticking out of the block(tried the 'extractor' or w/e u call it to no avail so i took the front cover off for better access). Now I try to go at it with the vice grips, and it won't turn...all it does is the vice grips jus spin around on the remaining part of the bolt...anyone had this happen? or jus know somethin i can try? Any help is appreciated...thanks