Hayes brakes come with a 2 year warranty so if they are defective you could always get them replaced by Hayes without dealing with that dealer again. If the bike is a great deal then buy it and get the problem fixed. You will probably still be out ahead. If you are still unsure then give Hayes a call and tell them your story, maybe they can be of some assistance or give you some pointers on what exactly to look at. Their consumer number is 1-888-686-3472

-Ryan