Cold start noise: worn out alternator bearings? 2006 2SZ-FE

[ThinkPad]

New year, new noises/defects.

https://youtu.be/t8LSnVCurLw

Cold starting the engine on a winter morning (2℃ / 35℉) produced this noise. I suspect this might be the bearings of the alternator? After the engine was warmed up a bit i didn't hear it anymore. I have driven around 40 mins on the highway and thus the engine was warmed up nicely. It ran smooth without any weird noises.

[ex-x-fire]

Some engines are noisy when they are very cold, you can remove the belt and try it out. Then listen to see if the noise is gone.

[nortonfb]

Belt slipping

[ThinkPad]

Belt slipping

Sounds plausible, as the belt was squealing a little bit a few weeks ago when the A/C compressor got engaged.

I will loosen the tension on the belt so i can rotate the pulleys etc. by hand to check them. And if those seem ok i will tighten the belt again.