I changed the two front copper brake lines over the weekend which went fine. When bleeding the system the nipple on the rear drum sheared off, it didnt turn so is not leaking any fluid. I just did the two fronts and the brakes feel ok. My question is, is it ok to drive the car with the nipple broken off ? as i said its not leaking fluid. Also what will need to be changed to fix it? i guess that the nipple and the union hold the piston onto the drum so will it be secure enough with only the union in it.