Bought Ford F 150 in 2010 new. Now has 178000 miles. just recently the radiator fan runs very loud. Should i just replace the fan assembly or is there something else I should look at. This is 5.4 engine.

 

Depending on how hot the coolant and engine are , the fan usually just lopes around until radiator cooling is required. At just about any temp except hot, you should be able to turn the fan by hand with slight resistance. I would suspect the lock up feature of it is stuck in the locked position and when you go to turn it , it will probably have a lot of drag and if so will require replacement. Some have a viscous material that resists flow when hot and others use a temp controlled spring.