Hey, I have an '04 E-320 and I have the following problem. I want to pin down the cause so I can take it to a mechanic and tell them what they should look at.
There is a humming noise that changes with the speed the car is going at. I have recently noticed that the humming gets more intense as I veer left. It is more noticeable at slow speeds and it makes the car vibrate a bit. The humming starts slow and increases in frequency until it blends in with the road noise but it can still be felt in both the steering wheel and the pedals.
The humming is not constant, it sounds something like voom...voom...voom... and the frequency varies with the speed.