A California attorney could advise best, but your post remains open for three weeks. As a general matter, private sales often tend to be "as is." I'm sorry for the difficult situation the purchase has put you in, but unless the seller included some form of written warranties, assurances, or representations as to the sound mechanics of the vehicle, or took measures to conceal something or other deceitful or fraudulent actions, these situations tend to leave a buyer with little recourse. You could consult with a California attorney to see their take on it - they could give you the most meaningful assessment based on state law. But keep in mind that as a GENERAL matter in many of these private sale settings, it could sometimes be better to cut losses rather than compound losses in pursuing remedies that carry uncertainty. Good luck
Tim Akpinar
