If you purchased a used car without having it inspected by a qualified mechanic, and the seller did not imply or offer a warranty on the purchase, there isn't much you can do. When looking at cars sold "as is," it is very important to have a pre-purchase inspection done by your own chosen mechanic. A $50 inspection could save you several hundred in repairs when ruling out cars that would be a very bad investment. If the seller won't allow you to have it inspected, or only lets you have an inspection done by their mechanic, that's a big red flag that you might want to walk away. Sorry about your luck on this one.