I sold a car to someone private party. The car had not been driven in several months, and I disclosed this to the person whom I sold it to. Hence, I did not know if anything was wrong with it mechanically, but the car was in running condition. Which was also discussed with the buyer. In California the seller is required to smog the car prior to selling it, I believe unless you sell the car as is? Anyhow I had the buyer sign a contract saying that I was selling the car as is and that the owner was responsible for the smog. The car was sold to a teenager and apparently a couple of days after the purchase the car over heated and they continued driving it causing the engine to blow the head gasket. Now they are harassing me and calling me several times a day asking for a refund. I told them that the car didn't have a blown head gasket when I sold it to them and that why do I have to pay for their mistake? Now I came home and they are suing me. Does their case have any merit?

You have a signed contract selling the car as-is. That should win the case for you.