2008 BMW E90 / 323i Weird Engine Whirring Sound

Today, my 2008 BMW 323i started making an unusual sound when I accelerate. I’ve owned it for less than a week, so I’m not very familiar with what the engine should sound like, but it drastically changed today.

I drove 5 minutes to an auto parts store to buy a new turn signal bulb and washer fluid, and the engine sounded totally normal.

I filled the washer fluid reservoir and replaced the bulb, and then when I was driving home, almost immediately the engine sounded really weird, like it’s wheezing or having a hard time breathing.

At first I thought I maybe spilled some washer fluid on something, but there doesn’t really seem to be much around that area that I can see.

A few specific things to note:

• the sound happens even when I’m in neutral and just putting my foot
  down on the gas pedal, and does not need to be moving to get the
  noise
• the noise doesn’t seem to happen while it’s idling, but

Here is a video of the engine running, and you can easily hear the sound while it revs up:
https://www.youtube.com/watch?v=H8o_RqQ6WDY

I’ve been googling and watching youtube videos about these BMWs with whirring sounds, but I haven’t been totally sure if it was the same sound, since the audio quality of most videos is pretty bad, especially while driving.

Has anyone heard this before? It will be a few days at least before I can get into a shop.

UPDATE Nov 19:
I brought it into a BMW specialist and they showed me that there’s an area under the engine cover where oil is leaking, and said there’s definitely something weird going on in the engine. Will update again once I find out what it actually is!