Buying a Car at Auction?

I recently purchased a utility van at the auction. I had 48 hours to take it to a mechanic to have it checked out to make sure the transmission and engine were in good order, but had to put down 70% before I could take the van. I made the mistake of going to a mechanic they suggested which was close and he said everything looked good except for the tie rods.

I drove it home to clean it out and found small rocks and dirt in the back along under the floor mat. I soon realized that I had been sold a flooded vehicle. Does anyone know if there is anything I can do to get out of this commitment on the van before I pay the other 30%? Any advice would be great. Thanks.

By JD from UT