Whistle noise during acceleration
The last few days I noticed that during acceleration (with any gear selected) i hear a "whistle" or "hissing" noise from the engine bay.
This "hissing" may be similar to that of a compressor or a turbo
The noise is very weak and I only hear it with the windows are closed.
The noise is still there when I am cruising with steady speed, but is weaker.
When I hear the noise(on the move) and press the clutch (therefore isolating the gearbox from the engine) the noise stops (the gear is still selected though).
When I release the clutch (thus connecting again the gearbox to the engine), the noise starts again.
When the car rolls without any gear selected the noise disappears.
While driving in the city the noise is not stronger due to echo from the buildings.
The Clutch assembly(with the DMF) was replaced last year.
The gearbox seems to work fine (did not noticed any issues while selecting gears).
I have a "939" 3.2 JTS(naturally aspirated) Q4 with manual gearbox.
I will visit the official dealer's garage,but it would be nice if i had an idea of what may be happening.