Here is a video of the noise
I just got I just bought a 04 BMW E46 330i with the sport package from a little pot lot. It sounded alright when we got it but then it makes this wobble rotating slapping noise only at idle and when I rev the engine it goes away. When I put my foot on the brake and give it gas it goes away. I have been told that it could be a loose timing chain. It doesn't sound anything like vanos rattle. the noise diminishes quite a bit. Also the engine does not make the sound right at start up usually when it gets to normal operating temperature does it start making this noise.
Things I have already checked or changed
-radiator flush but not the engine block flush
- changed the oil
- belts and pulley all are good
- fan clutch seems to check out fine
- I have heard it could be vanos seals but that is a different rattle from what I can hear.
- doesn't knock with acceleration so don't think it is the rod knock
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