always use a 6 point socket never a 12 point wrench or socket, tap around on the bleeder with a hammer to try to break it free, put some heat to it and do the same thing. give it one good wack with the wrench or socket on it, hard and fast. either one of 2 things is going to happen, its going to break free or its going to break but either way if it breaks then just drill it out, tap it and call it a day. wat car is it on anyways