Have you done anything to address the water damage? At the least, all of the components need to be inspected and cleaned with rubbing alcohol. Check all components for any signs of corrosion. Verify that the sockets for the LCD cable socket on the logic board free of corrosion and are still firmly attached and have not been loosened in the slightest. If they are loose, then the display will not be making good contact. Precision micro-soldering would be required to repair this issue.