This is about my E320

I have had this sound since I bought the car and its surely not changed its volume or pitch in the last 18,000 miles of ownership.

I removed the serp belt to test - and the noise was still there, I then used my stethescope to test all parts and the noise is only heard from the front lifting eye of the engine (through which the air pump is mounted)

its a rythmic very low volume scratchy sound like a dry bearing of sorts - The pump is in good shape as it makes its own little machine noise when running and then shuts down.

Im guessing this sound is being magnified by the lifting eye as it is acting like a tuning fork. You can actually hear it if you put your ear near the engine top with the plastic cover removed.

I showed it to a couple of mechanics and one said its a balancer wheel or timing chain problem. The other never heard anything like this.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)