I purchased a new belt tensioner for my car and I am having problems removing it because the bolts are rounded. Apparently, someone that owned the car before me tried to or did use the wrong size socket when removing the tensioner. I am trying a 15mm which is too big or a 14mm which is too small. I have tried using a file to make the bolt head smaller and I am still unable to get any wrench or socket to fit. I am almost ready to get my torch out but I need the bolts for the new tensioner. Any thoughts on the matter? Thanks in advance!