So basically i bought an 08 TC.. I washed the car for the first time about 3 weeks after i bought it. It was a HOT day.. does water and soap mess up the brake pads? cause ever since then.. there is a grinding sound on my back two brakes.. I took my car to the dealership asking them to check out the sound.. all they fixed was the rattling on my exhaust and didnt evev check the brakes.. Dealerships dont do anything... So, to this day i still have the grinding/scraping sound on my back brakes.. The pads arent even worn out yet.. what could it be?

are there any strange scratches on your rotors?

They are not "strange" but yes..there are scratches ..slightly zig zagish in a way..

Did you try to wash the brake system?

try bedding in the brake rotors and pads again:
http://www.nurspec.com/ProductInfo.aspx?Imge=4

You might be able to burn off some gunk that got in there.

Brake rotors will develop a coating of rust after a car wash so you just need to apply the brakes more aggressively a few times to clean off the rust.