I'm having an issue on my 04 GT. I just recently replaced the idler pullies and the belt in order to try and fix a squeaking noise that was happening in my belt drive. After I did that and started the car up a bigger noise started, it sounds like the car has a supercharger when it doesn't. I pulled the belt off and started it up, no noise. So something on the belt drive is making a loud noise. Happens at all RPMs and gets louder. I put the old idler pullies back on to see if it was the new pullies and the same noise. Ok, so I spin all of the accessories by hand and the only thing out of place is the water pump. When I spin the water pump manually it sounds like a groaning noise, kinda like rubber on rubber. Spinning it fast by hand you don't really hear it, just slow. I wish I could spin it to engine speed to see if it was making the noise. I tried to get a water pump at Autozone but as usual they are useless. They had to order a part from another store. Today I show up to get the part and it's not even close to being the right part. While I was there I had them test my alternator, so I don't think that's the source. None of the local part stores have a water pump for this car and ford of course is closed today and tomorrow. Anyone have any ideas? Could a bad water pump cause this loud supercharger type whine?