Loud Whistle or screeching noise 2011 328i , 70k miles

[Chip5]

Hi, one fine day recently ......... my perfectly running 2011 328i starting making an awful screeching noise under the hood and rough idle! I immediately looked for a bad idler pulley, belt or AC issue. However after a bit of research and inspection I have all but ruled those out as the culprit. I then blamed the VANOS and replaced them, still no luck. Next my YouTube based research led me to believe it is a bad valve cover not allowing it to breath correctly? I did do a test - I let it start screaming then removed the oil filler cap with the engine running- i did notice a change in the idle ( not better just a change) Should i replace the V/C? Also I do now have a ck engine light on - i will scan it tonight if my Bluedriver will scan a BMW? if not what does everyone recommend for SCANNER FOR THIS MODEL? I also ran across an article which mentioned this could all be caused by a bad gas cap? since no fuel has been added since we began this. I will try running it w no cap on next. Ideas?

[marvinstockman]

Removing the oil filler cap will change the idle, as it allows extra air into the engine.

I would remove the drive belt, and I would see if your screech goes away. While belt is off, turn all rotating devices by hand to check for roughness.

Does noise go away when AC is off?

[jclausen]

Removing the oil cap when running would be to see if the noise changes or goes away had it gone away it would have meant the pvc valve build into the valve cover we bsd, the idle will change because your introducing a huge air leak, lean fault could not be present, try removing the belt as mentioned as above to see if the noise goes a way. Is ther oil leaking around the front of the engine

[Chip5]

Removing the oil filler cap will change the idle, as it allows extra air into the engine.

I would remove the drive belt, and I would see if your screech goes away. While belt is off, turn all rotating devices by hand to check for roughness.

Does noise go away when AC is off?

Hi Thanks!, the sound is still there with A/C on or off and does not alter with RPM change. I will pull the drive belt and check- however since it does not make the sound until it runs a bit, I have a suspicion we may be looking at some vacuum caused issue. It seems a lot of mechanics advise changing the entire valve cover assembly. Hmmm Seems fun...........

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Also no oil leaks i can find

[gusm325]

Can you post a recording?

[JDStrickland]

Hi Thanks!, the sound is still there with A/C on or off and does not alter with RPM change. I will pull the drive belt and check- however since it does not make the sound until it runs a bit, I have a suspicion we may be looking at some vacuum caused issue. It seems a lot of mechanics advise changing the entire valve cover assembly. Hmmm Seems fun...........

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Also no oil leaks i can find

This is not a logical conclusion given the symptom set you have defined.

[White94RX]

You need a new valve cover.