Hopefully someone can assist with where the noise is coming from.
Might have a leak, intake. Or, exhaust, but maybe not if misfires.
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Silentus, what was the solution to that noise? I have the exact same problem, and it comes and goes.
Ok when this happens pop hood open and try to open oil cap if you can't open or has a lot of pressure most likely crankcase vent value, mine does it once in a while ill end up changing it sometime!
Hello All,
I just went through this. If there is a large vacuum present making it difficult to remove oil cap this is a crankcase breather problem. There is so much vacuum being created that it is sucking air through the main seals creating the whistle. Not positive it is through the main seals but somewhere creating whistle. This requires a replacement of the valve cover because the CC breather vent is integrated in the cover. If you do the Valve Cover yourself make sure you have a good torque wrench and if you go over the torque specs don't back off the bolts or you will have to replace them. Great video to understand what I mean:
This was my original thread, scroll to bottom for results: http://www.bimmerfest.com/forums/showthread.php?t=745998
Yeah definitely a sludge issue. I've seen mixed feelings on additive to clean engine etc regarding seals and such. I did notice the sludge dissolves with new oil so short interval oil changes may help. I also noticed after replacing the valve cover, it sucked up about a quart of oil. That leads me to believe oil stays up there, turns to sludge and then starts falling off and accumulating on the head until new oil washes it away. Just speculation though.
Some thought pulling the cover and doing a cleaning might work too, for me it was just easier to replace the cover.