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The sound is now back. It came back within 50 km of driving with BMW oil.
It has now been about 300km and the sound remains. However, it does not seem to be clicking at idle. Only when it is above idle does it occur. It is most apparent between 1500-2500 rpm.
It only occurs once the engine is at normal operating temp, and cannot be heard above 3000rpm.
I have a really hard time believing that it is the heat shields. It has to be coming from inside the engine. I've read all the threads I can find on this noise (there are several) and watched all the youtube videos (there are several), and it's amazing that there has never been a solution to this.
The fact that it is random and arrhythmic makes me think that it is not a lifter.
I am wondering if it is somehow related to the vanos. I understand that it is controlled by oil pressure, and i'm wondering if there is insufficient pressure until 3k rpm...or changing oil somehow elicited a small problem that was made worse by changing the type of oil.
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