For a while when I pull the front brake I could hear a faint buzzing noise come from the front master cyclinder. Yesterday I replaced the front brakes and now I hear the buzzing alot more, more after about 15mph for some reason, if I just very lightly touch the front brake the sound kind of fluctuates. Pads don't seems to be rubbing the rotor ecause I can cruise around for a while and come home and the front rotor isn't hot. Any ideas?