Hi all, I've got a few issues to work through on my 2007 3.0 Z4, and this is one I wanted to check with you on. Recently, I was in a big hurry to get somewhere, and thus was driving at higher than normal revs for about a 8-10 minute interval(~6000, give or take). Several stops and starts at lights, and then fast acceleration. A few minutes in to this trip, I heard a sound I have never heard before. It sounded to me like the sound of an electric fuel pump running, but it only did it when the throttle was depressed; if I coasted, I never heard it. It sounded like the fuel pump running in my 240z. Is this a problem, or is that normal behavior under such conditions? I was literally driving with the throttle full stop on acceleration, from every stop. Thanks for any info on that sound.
Possibly fuel pump struggling to keep fuel pressure up because the fuel filter is clogged enough that at high extended rpm’s the issue shows up.
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And you are 100% positive the sound was coming from behind the seats? I would guess a serpentine belt or maybe a tensioner making the noise. I know this sounds crazy, but check the cabin filter? Buddy of my kid had one that was so dirty that when he would go fast(80mph+) it would push down with enough pressure to rub on the fan causing a strange sound.
I'd try to replicate the sound while in the garage or some place quiet to isolate.
If I remember correctly, you have to drop the exhaust to replace fuel filter?
Might as well replace the pump too while you have it apart.
https://www.pelicanparts.com/techart...eplacement.htm
Or it could simply be a new onset leak in the exhaust system that was triggered by the high pressure from high revs. I have seen this happen before in non-BMW vehicles especially at the junction between the engine and manifold. It could also be a small new leak in one of the exhaust pipes or boxes that currently only becomes noticeable with high pressure/revs! If so, it will get louder and more prominent soon.
Or it could simply be you are just not used to the engine/vehicle sound at this high rev range and there is absolutely nothing abnormal!
I wouldn’t worry about this sound unless it recurs. And if this happens and it becomes reliably reproducible then I would take the vehicle somewhere where there is a lift and give it a good inspection while engine is running/reving to pinpoint where the sound is coming from.
Last edited by tekoo; 10-26-2018 at 08:43 PM.
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