I recently sold my Volvo V70R wagon to a Texas buyer. He had a prepurchase inspection performed on the car post purchase prior to the long drive back and the mechanic found no problems.

Once back in Texas he replaced the tires which were near gone (without prompting I had lowered our agreed upon price to compensate for same) and discovered the noise we all thought was related to the worn tires was in fact a wheel bearing. I learned this from a forum post.

I offered him a used factory load bar set with a new value of a couple of hundred dollars as compensation. This is a guy I will never do business with nor even see again. There was a "as is" clause in our purchase agreement but felt it like the right thing to do and it felt good to do it.

Your case is not exactly the same. Once the problem is determined you will have a decision to make.