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2003 W220 S350, Eu Spec
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Discussion Starter · #1 ·
When I drive my 2003 W220 S350 non-4matic (eu netherlands spec), mainly with colder engine, I hear a whistling like sound only between 40 and 43kph in 3rd gear. Sounds like a fuel pump pumping fuel with air. It is only at that speed and at constant speed or very mild acceleration. Normal acceleration and you don't hear it. That speed and in 2nd or 4th gear and nothing is heard. If the engine is really hot then the sound is there under the above condition but a lot less loud.

The sound is not there when the engine is cold. It start from about 50 degrees celcius coolant temperature. When everything is really thoroughly warm the sound is also almost gone. So from 40 - 43 kmh. Gas off / coast and it is gone, only audible at 10-30% throttle. More and the sound is also not there. And so only in 3rd gear

Could it be a resonance in the driveline? Anyone who has experience with this?

For the rest the transmission works fine. Shifts well and has just had an oil and filter change.
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