Loud Squealing

[Tomcat3481]

I have a 2011 528i that when it gets warmed up a liud squalling noise comes from the belt area of the car. The belt and tensioner have both just been replaced thinking that was source. The problem has continued and can find nothing else wrong. Just noticed if i stop the car and turn off the engine then restart it in 30 seconds the nouse is gone but qill reappear after a short drive. I have ruled out the alternator as well. Any body have any ideas?

[White94RX]

Probably time to replace the valve cover. The crankcase ventilation diaphragm goes bad, leaks, or tears, and then the crank case pressure is wrong. Air starts being sucked in through the front crank seal, causing the noise.

You can confirm this by removing the oil cap while it is making the noise. If the noise stops, then you confirmed the issue.

[jclausen]

With the engine running and the noise happening remove the oil cap just a bit does the noise change

[Tomcat3481]

Thank you, and that was it. I am a do it yourself kind of guy but the to that is knowing when to say when. Took it into the BMW dealer and they said they had a bulletin on the VOS sensors so most of the labor costs will be taken care of. Still a $700+ valve cover is expensive. Thank you for help in diagnosis if the problem.