My 97 E420 has 104K miles. Recently,I discovered that when I drive the car for 15 minutes in the morning, I do not hear any driving noise. However, after that, I start to hear low pitch "goo, goo...." driving noise seems coming from driver side under the hood regardless I drive straight or turn the wheel to the right and left. Before I have got this annoying driving noise, I had both right and left control arms bushings, and lower left ball joint replaced due to other noise. I can not tell whether the new noise is caused by the left wheel bearings or the upper ball joint of left control arms. Therefore, I took the car to the local auto shop and MB Dealers for help. Both the local auto shop and MB dealer can not locate the problem and find the resolution for the problem. Is anybody having the same problem as I do? Your kind professional recommendations to resolve this driving noise is greatly apreciated. Thanks,

Have you tried having the tires moved from 1 position to another??

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Thanks to Mr. M.B.DOC, Yes. I just had tire rotated and balanced about three weeks ago.

Mr. MB DOC. I just got the 4 tires rotated yesterday and still have the driving noise. It seems to me the noise coming out as long as the car is moving now. Is the noise possible coming from the upper ball joint, wheel bearings, or power steering? or Anything else? Thanks,