[Nicholas330i]

Upon starting my 330i, there is a faint noise coming from the front of the engine.

I replaced my water pump within the last year, and haven't been driving much recently. It doesn't sound like what my water pump sounded like when it failed, and there's no coolant leaking.

I used a stethoscope and couldn't pinpoint where the sound was coming from, but it sounds like it could be the alternator pulley. I thought it was a belt but I'm just not sure. I'll attach a link below. Second opinions are appreciated!
NOTE: The noise disappears after the car has idled for a few minutes.

Update: It is now a light squealing sound.

 

[dmax]

Sounds like a pulley. If one is bad, replace all three--two tensioner and one idler puller.

Alt bearing don't really seem to go bad. The PS pump pulley's shaft can loosen and pull out...so when belt is off, check it out too.

Good time for new belts, but if they're new, make sure you put them back on in the same direction--they remember.

 

[Nicholas330i]

Sounds like a pulley. If one is bad, replace all three--two tensioner and one idler puller.

Alt bearing don't really seem to go bad. The PS pump pulley's shaft can loosen and pull out...so when belt is off, check it out too.

Good time for new belts, but if they're new, make sure you put them back on in the same direction--they remember.

Got it 👍 I'll remove the belts and check the pulleys. Are both tensioners the same size?

 

[dmax]

Got it 👍 I'll remove the belts and check the pulleys. Are both tensioners the same size?

Same size, but different pulleys. Realoem.com enter your vin, go to town. Also search here--bmw doesn't show a pulley separate on the mechanical tensioner if you have one, but you 'can' get the pulley. Part numbers are around here for all of them too.