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- Chrysler Pacifica (https://www.chryslerforum.com/forum/chrysler-pacifica-15/)

- - Noise is back (https://www.chryslerforum.com/forum/chrysler-pacifica-15/noise-back-30447/)

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. 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. I haven't heard the noise fur 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

Listening to it again, that sounds a lot like a bearing failing on something.

Mechanic couldn't figure it out

Replaced serpentine belt and still does it from time to time. Once a week or every couple weeks. Only when I'm doing a lot of stop and go within 10 minutes of driving and shut off car and makes the noise at shut off and start back up and runs fine.

It is a bad bearing, a belt would never make a sound like that.
The initial part of that sound is the give away for that. I have heard it before with a bad bearing, but you have to figure out where.
Most likely the alternator, ac, or an accessory pulley.
And yes, the sound can some of the times go away for a bit.

Even with the alternator being only a year old almost? I asked my mechanic about the tensioner and he said it was fine

As was offered in previous post...something is causing it and you were given "likely" culprits that need to be checked. There is also the possibility that the TIMING BELT TENSIONER is going bad. And that takes a fair bit of disassembly to get at to check.
Good Luck!