If took out a car loan for someone. They could not co-sign dut to bad credit. Can I sue if they stop paying me back?

No, by signing the contract as a co-signer you automatically accept the responsibility if the signer is not paying you will be financially responsible for the loan. There is no legal action you can take against the signer. For more information you can visit http://www.autocreditfinancial.ca IN some states you can recover your lose through small clames court you will have to check the law in your state.You can do this by looking on the net by pulling up your states general statue laws.