Recently my motor has developed a very annoying and potentially troublesome symptom. It started more or less suddenly some 1K miles ago, first noted when starting the car in order to leave for work one morning.
It's a whining/whistling noise that climbs and wanes with the revs. It's not audible at all at idle, barely audible between idle and 2K rpm and quite noticeable above 2K rpm unless pressing the accelerator aggressively, when it's either not audible or altogether gone (quite hard to tell the difference for obvious reasons). As it follows the revs, it disappears completely whenever pressing the clutch during gear changes.
As far as I can tell the noise is whining or whistling (sounds almost as if the car was equipped with a supercharger or turbocharger) as opposed to rattling or clanking. It's ever so slightly less pronounced when the engine is hot, but the difference is negligible.
The noise is distinctly coming from the engine bay, probably on the intake side of the engine - noise is next to inaudible during idle, and it's kind of hard to listen under the bonnet while driving.
It's obviously quite more noticable with the windows down, or from the outside of the car.Reading about similar issues on general BMW boards pointed to a leak somewhere in the intake hoses. The usual culprit is however specific to BMWs and not present on our Alpinas, I also had a leakage/smoke test performed that confirmed there are no leaks whatsoever.
Mileage is just above 90,000 kms / 56,000 miles, the car has always been serviced with Alpina specialists ahead of schedule with oil and filter changes in between. An intermittent error light for the rear fog light aside, there are no error lights and no error codes. The car drives more or less like normal, perhaps a tiny bit on the sluggish side compared to earlier, before this symptom started.
I would really like some assistance with this, as Alpina specialists are few and far between in Sweden, and BMW specialists are, for whatever unknown reason, usually very reluctant to deal with Alpinas.
