[masraum]

Most used cars are "as-is" unless otherwise stated. Unless you can prove that the person that sold you the car intentionally defrauded your BIL, then there's nothing that you can do.

"he was driving it on weekends and having fun for a few years" Besides, if he's had it for a few years, or even if he's only had it for a few months, the leaks and headstuds could have been broken since he bought it.

Did he get a pre-purchase-inspection done on the car by a reputable shop? It sounds like he did not.

I'd say that he should get the Porsche fixed and write this off as a valuable and important life lesson. Caveat Emptor!