hey,

Im having the EXACT same problem. That loud noise coming from the fan when the ac is turned on or when just running occasionally. I replaced thermostat and it fixed overheating problem but i heard the noise again this morning. I determined that it was the fan and I am in the process of searching the fan for any sticks or twigs. Let me know what you find out about replacing motor.
...also the fan assembly is a ***** to take out due to engine mounts.

 

hey what i did is take off the metal plating thats on the fan and use a large screwdriver to pinpoint the noise, i always find leaves in my radiator or engine bay...even if im no where near a tree.....but i really dont want to take the whole radiator out for this but i will have to replace it eventually Also i dont have an overheating problem but my hoses are not pressurized when the car is on...the futhest my car goes is a dash below the half way point but i will keep in touch and let you know how this goes