W210 4-matic annoying droning noise from left front

[Rob Pruijt]

My car makes a very annoying droning noise that seems to com from the left front wheel.
When it is warm outside the noise starts after a few miles, when it is colder, it takes up to 10 mls before it starts.

A sample of the noise is in the following link:
http://test2.ergonomie-advies.nl/images/Noise.mp3

1. It is slightly intermittent, sometimes is stops for a few seconds.
2. With microphones under the floor insulation, I detected the loudest noise near the accelerator pedal.
3. Rotating or changing tyres has no effect.
4. The tone does not vary with speed.
5. Changing directions has no effect.
6. It is louder when cruising.
7. On a lift (with all wheels off the ground), there is no noise.
8. I also blocked three wheels so only one wheel is turning, still no noise.
9. I even used axle stands to keep the axels horizontal, still no noise.
10. The rubber parts of the control arm are still somewhat flexible.

Who recognizes this sound?

Rob