My tech has one mentioned to me that this is typical of the D3 engines - but I would really like to know where the sound is coming from. When searching for D3s on youtube I can actually hear it in others as well.
If you listen at 3:24 in this video you will clearly hear the rumble/vibration I am talking about. Please note that you must use headphones since it is a very low frequency that phone/tablet speakers can't reproduce.
Just after he switches on the ignition in this video you can hear the vibrating rumble as it comes and then disappears. I'm not talking about the normal "engine hum" - there is another very low pitched rattle which is present for like two seconds.
https://www.youtube.com/watch?v=ivam...pPy8qg&index=6
What the hell is that sound? It is driving me crazy... It does not have to do with the suspension, and we have changed just about all the engine mounts...
And it is mostly/only present when the car is warm