I have a 04 f150 xlt 5.4 3v 88k
Has a grinding noise under the hood upon investigation I found a red power covering my belt traced the problem to the Ac compressor my guess is the clutch is trying to engage not sure why it's below zero for the last 3 months no need for the Ac any one have a problem like this any help would be great . Thanks

 

You found what covering your belt ?? Powder ?? like rust ?? The Compressor kicks in all the time even with the heat selected.

 

Found out it wasn't the Ac it was the belt tensioner bearing had fried guessing it was burnt grease the pully was so shot it was starting to score my block in the pic behind the pully you u can see it

 

Little better pic of were the pully was

 

Well that's cheaper and easier to replace than the AC compressor.

I had '92 F-150 that the AC compressor pully/wheel sheared off on. It was winter (snowing & muddy) and I was comming out of the woods (hunting) when I head a loud screeching with smoke coming out from the hood, quickly followed by a POP! Of course this was in the middle of nowhere on a Saturday morning. And the adventure began...