It's very hard to prove fraud, which requires material misrepresentation of fact which you reasonably relied on and which caused you damage. If it's intentional fraud you have to prove that they knew and deliberately told you something other than the truth.
Here, you won't be able to prove the misrepresentation or the reasonable reliance. Used car dealers are notorious for going out of their way to not now anything they'd have to disclose. Your question states that your dealer denies knowing anything, which means they didn't misrepresent the condition to you, they just didn't know or disclose this damaged frame.
That's why used car sales are usually "as is," which means all the risk and all the respondibility falls on the buyer. The seller's not the one who has to investigate the facts and disclose them to the buyer, it's the buyer who has to "beware" and do their due diligence. They have to get their own mechanic to inspect the car and review the CarFax report and the maintenance records and test drive the car BEFORE buying it. Here, your own mechanic woud have discovered the frame damage, so you didn't do these things, and you will have a hard time proving that your reliance was reasonable.
You can hire a lawyer to review your sales contract and threat the dealer with a fraud lawsuit, but from these facts, it doesn't sound like it would be a good threat.
PLEASE READ THIS BEFORE YOU COMMENT, EMAIL ME OR PHONE ME. I'm only licensed in CA. This answer doesn't make me your lawyer, and neither do follow-up comments and/or emails and/or phone calls, and you shouldn't expect me to respond to your further questions if you haven't hired me. We need an actual agreement confirmed in writing before any attorney-client relationship is formed. This answer doesn't constitute legal advice, and shouldn't be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue.
You should talk to a Consumer Law attorney near you right away and find out for sure what your rights are. At $13,000, I’d be surprised if any car dealer didn’t at least do the normal safety inspection so the real question is whether or not that would have shown the damaged frame. You also need to find out if the dealer ordinarily runs a Carfax or AutoCheck on the cars they sell and then see for yourself what those sources say about your vehicle’s history. Wrecked and repaired cars can be dangerous because you don't know the quality of the repair job or the repairman. You can run a CarFax online yourself to find out more about the vehicle history maybe, but you need to know that it isn't always accurate. They get their information from lots of different places but it seems to be about 80% accurate, more or less, in our law firm’s experience. That’s better than nothing, although other title history services are available on the internet. Still, the existence of an accident on the CarFax report seems to almost always be accurate in our experience. If the dealer ran a CarFax (and the CarFax company keeps track of who runs their reports too), then it can be on notice of any accident record and all else on the report. If your report shows an accident (or any other negative info) before the dealer bought the car, then the dealer's report probably did too. Car dealers generally have a higher disclosure obligation than an ordinary consumer would have selling the car. If the dealer knows something and realizes that the buyer would want to know about it, but doesn't disclose it, in most states the dealer may be committing fraud by concealment. Every state has its own definition of fraud, but generally it's a lie or something kept hidden that costs you money. “What is Fraud” is explained in this Avvo Legal Guide: http://www.avvo.com/legal-guides/ugc/what-is-fraud-1. There is a big difference in value between a car that has never been wrecked and one that has, even when the repairs are done right. It's called "diminished value" and it means your car is worth much less than one that was not wrecked and repaired. You probably have the right to either cancel the deal or recover the amount you were overcharged for the car. If you want to know what your car is really worth, take it to a car dealer and see how much they will give you for it after you tell them that the CarFax for it says it was wrecked and it may have frame damage. Many car dealers won't want to buy it at all. Once you have already spent your money, it's not too late to have an independent repair shop inspect it and tell you what they think, but the best time is before you put down your hard earned money. Still, there is more than one way to get rid of a wrecked car (or a bad car) or to get even when you’ve been ripped off. You should talk to a local Consumer Law lawyer about your state laws and what your rights are, right away. Call your local attorney's Bar Association and ask for a referral to a Consumer Law attorney near you or you can go to this web site page for a Free Online 50 State National List of Consumer Law Lawyers (http://www.ohiolemonlaw.com/ocll-site/ocll-locate_local.shtml) and find one near you (lawyers don’t pay to get listed here and most of them are members of the only national association for Consumer Law lawyers, NACA.net). But act quickly because for every legal right you have, there is only a limited amount of time to actually file a lawsuit in court or your rights expire (it's called the statute of limitations), so don't waste your time getting to a Consumer Law attorney and finding out what your rights are. Before you decide to buy a used car next time, read this Avvo.com guide on How to Avoid Buying a Lemon Used Car in 7 Steps: http://www.avvo.com/legal-guides/ugc/how-to-avoid-buying--lemon-used-car-in-7-steps. If this answer was helpful, please give it a “Vote Up” rating. Ron Burdge, Attorney, www.SalvageTitle.info, www.burdgelaw.com
This answer is for general purposes only and does not establish an attorney-client relationship. Click the link to find a Consumer Law attorney near you.