Risk more money?
Is your car runniing OK now? I wouldn't put another 500 into the car. We wound up trading our BMW in at a non-BMW dealer. If we would have fixed the car, they wouldn't have given us any more money for it. If the problem isn' t terrible and you plan to sell it in the summer -- to a dealer -- then I wouldn't fix it. You won't get your money back and it won't help the sale.