The biggest concerns are related to the drive line. If the transmission took water in, the differential. That could lead to problems with bearing failure as well as other internal issues. Also, sensors corrode over time. The water can speed that up. Consequently, it may work when you get it back and then you end up with trouble a month from now. Rust is always a concern because the water gets into places that it shouldn't be and those area are not protected. Finally, wiring can be an issue. In your wiring system, there are grounds, splices in the wiring. If they corrode or rust, then you can end up with electrical nightmares.
I wish I had better news, but those are the types of concerns you need to be aware of. If it reached above the seats, keep in mind all the electrical components in the inst. Cluster, stereo, climate control, HVAC system, speakers in doors.
Tuesday, January 25th, 2011 AT 10:57 PM