I have been in this position or similar ones before. I would call the buyer and tell them of the situation. It is something you did not know about before selling them the car. I would offer to knock something off the price and let them fix it or give them the choice of sharing the bill with you. They will have a choice and if they choose the first, they can have their own mechanic do the work, if they choose the second, you were up front with them and they benefit from a brand new hb.

Of course they could choose neither and then you are simply back where you are now and you could choose to go ahead and fix it.

Either way I believe they will appreciate your honesty and having a choice.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.