2v 5.4 hi-pitch whine; fan clutch?
 

so we've had my wife's '04 expedition for a few winters now, and every year when the temps drop i'll get a random, short, high-pitched "whine"; it fades in and fades back out again. it's the strangest sound, almost eerie. it doesn't sound like hard surfaces rubbing, like a bearing or belt, but more of like a sound effect from a ghost movie, haha. for the longest time i thought it was air getting by the seal of the windshield, thinking maybe the cold made it contract and air would get by (only ever heard it at traveling speed).

well this morning i started her truck, and while walking back to the garage i heard it again, for the first time while not moving; it's coming from the front of the engine compartment, and it's really loud outside the vehicle, haha. i've thought for awhile now for other reasons the fan clutch has been acting up (thats another story), so i'm wondering if it could be something in that?

Does it go away when warmed up? I'm thinking if not the fan perhaps the power steering pump is protesting the cold weather.

no, not really. and it's not consistent or dependant on engine RPM either. it only lasts a half to maybe 3-4 seconds and is very intermittent. it's not like a constant whine... i guess the best way i could describe it is it sounds like an electronic "squeal", always the same pitch regardless of engine or vehicle speed. wish it was predictable so i could record it.