https://youtu.be/9N1ocdwnZB4

drive a 2006 Chrysler pacifica with 159,000 miles and at random I hear a rumbling noise under my hood while idling and when I turn off car. I hear a rotational noise like a rubbing / grinding. I go to start the car again and it has no noise. The car runs fine though. Usually within the first ten minutes of driving and in stop and go by getting stopped by lights The alternator is less than a year old cause I had a noise on top of engine in May 2018 and it was the alternator. The battery is 3 months old cause it wouldn't start my car when it was negative degrees out. I haven t heard the noise for about two weeks now and came back tonight. A video during it the best I could and a video when I got home of alternator at turn off listen very carefully in the videos or will not hear what I m talking about. please see link above. The oil I keep a eye on and make sure never low cause pacificas like to burn oil. It did it again and was able to get a video. Please see above.

Update

My mechanic put a new serpentine belt and it did it again the next day and then today again today. Took it back and asked if timing chain was ever done and not sure. Turns out this case is a belt. Not a chain. Thinking if timing belt. The car wouldn't run right at all.