2001 F-150 4.2L
171,000 miles

When engine first started in the morning, engine would immediately chirp/squeal very loud for 1+ minutes. Sounded like a slipping belt. Noise at front of motor somewhere. No 'check engine' light or codes. Engine starts & runs fine. Over 2 weeks time, noise got a lot louder & lasted longer. Figured it was a defective new belt (belt was 1 month old) or a pully bearing went bad. Took belt totally off & rotated all pullies by hand, no noise. With belt off & engine cold, turned on vehicle for 5 seconds. Only crank turning. Noise still there. Hmmmmm...... weird. Figured only the worse- main or cam bearing? Crap, engine shot. Drove to non-dealer shop to get an expert opinion by 'The Man'. The next day they said it was the problem stated in title. $300 later, engine very quiet & no issues.

Sample of the exact noise:
https://www.youtube.com/watch?v=ge3S0xIMm3o
https://www.youtube.com/watch?v=-OPa...eature=related