Whining sound BMW F30

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My car sounds like airplane taking off on cold starts. It sounds like it when parked or driving. Increasing revs gets louder.

Could it be alternator bearings? The sound is hard to find where its coming from.



Water pump replaced due to bad pulley.

Alternator clutch pulley replaced.

New belt on.

Only pulley has slight movement is AC compressor pulley.

BMW 320d F30 2012


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igorsbmw 1 week 11 Answers 78 views Member 0

Answers ( 11 )

  1. Hello

    Have you tried to start the car without the belt? Is the sound gone then?

    A common problem is the alternator that is making whining sounds, yes.

    Normally I use a tool like the Powerbuilt 640582 Mechanic’s Stethoscope link to amazon to diagnose this problems easily. It’s a common tool in any mechanic workshop, ask if you could lend it from a workshop 🙂

  2. What about secondary air pump? The noise sounds as jet for about 10 minutes and goes away. Is there any way to troubleshoot it. I have a feeling it could have some water in it as dealer washed the engine before he sold it to me. Can it be cleaned?

    Idea starting engine without belt is good.

  3. Because of the ” Increasing revs gets louder ” it sounds more to be a part of the multi rib rim.

    What if you turn off/on the air condition? Any difference?

    Any video of the sound?

    Anyways, I think to remove the belt is a good solution to find out if it comes from that place or not!

    Edit Forgot: Secondary air pumps are fitted to petrol engines

  4. Video is above. Or click here https://www.youtube.com/watch?v=5z-Mf-mNgO0

    AC on or off is the same, so its not AC compressor.


  5. The reason I say it could be sec air pump as the noise goes away after 2 or 3 min. The sec air pump runs for that sort of time. I need to check if there is any leaks on hoses or underpressure hose to the check valve.

    But then again I dont have engine check lite on

  6. Are you sure? I need to check that as it lists sec air pump on eurocarparts for my car.

  7. If that is alternator the why noise goes away after 3 min. I know the loud is increased on start but it still spins the same isnt it

  8. I think you should start with to remove the belt, listen if the problem comes from there.

    If it does. Lend or buy the stethoscope tool that I linked too and you’ll find the problem within 5 minutes.

    No need to guess things and waste money on parts you guessed was faulty.

  9. Thanks, I will get the tool

  10. Just checked voltage on my car on cold run. Now it sits at 14.2 V

    For 5 min it was jumping up and down to lowest 12.7 V

    Is there possibility that bearings warmed up and it’ running freely or what else is the problem

  11. now when idle when accelerating it drops down to 12.7 and goes back to 14.2

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