2005-2009 Belt squeal
So when I purchased my 05 gt from the dealership I test drove the car with my wife and noticed a very annoying belt squeal at about 2500-up rpms and I told the salesman about the issue and he advised me he would have a technician fix it up for me. The Ford dealership put a new belt on and the sound dissapeared for about 4 days and then came back so I pulled off the belt and started checking pulleys, replaced the tensioner pulley and all 3 idler pulleys and once again the noise went away for about 4 days then came back. So at this point I checked all the pulleys again and noticed the power steering pump pulley appeared to be out of alignment so I took it back to the dealership and they re-pressed it on for me into the proper alignment and the noise dissapeared for a few days and boom it's back again. So I pulled the belt back off and was just baffled about this checked everything again then I went to put the belt back on and noticed the belt was hard to get on the power steering pump pulley due to a metal guard that runs directly above the power steering pump pulley and protects it from touching coolant hoses. I bent this guard up a little to give more clearance for the belt and pulley and boom the sound is gone now for several weeks. My only guess is that the belt was either touching this guard and squealing or the pulley was touching the guard causing the belt to squeal on the smooth idler pulley but this guard was the culprit for sure. If you happen to have a 5-speed that will squeal when at WOT and shifting gears you might want to check this.
Black 2005 GT 4.6L 3v SOHC 5-speed, 3.55's k&n drop in