I'm having a hard time isolating an engine squeak on a 1989 190D with 149k kms / 95k miles. It is the high pitched sound you can hear in this video. https://m.youtube.com/watch?v=CzXPx5Z4iPQ

To my ears, I thought it was a failing bearing on the belt drive. It is more noticeable when the weather is colder, and more noticeable for first 10 minutes. However, it is generally pretty bad - you can hear it going down the street.

I moved the camera around for the video, which is representative of what I can hear :

- It is louder on passenger side than driver side
- It seems to be coming from the front, loudest when you are right over top of the head.

I replaced a couple of parts that we old anyway, just to try to fix:
- New alternator - old bearings had made some noise, but not terrible, and was smooth
- New waterpump - old one felt a little lumpy when turning
- New fan clutch
- New hydraulic shock on the belt tensioner (old one was leaking)

Also, the AC compressor is recent.

Any other thoughts about what this could be, or ways to diagnose? I'm somewhat stumped.

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W201 1989 190D