You dont think if you make them take the car back they will be grateful that you now have given them a running car that they can sell for more money? I dont see how they have any incentive to pay for the damages, since they already have your money and are holding the title. I know it sucks that they damaged it but I dont think they will do much to help you out since they already have payment.

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02 e53 X5 3.0i Manual Trans
13 e70 X5 xDrive35i
04 Honda S2000