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      08-13-2019, 08:35 AM   #1
NYG
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What is this sound coming from my M4 at 1800-2000 rpm? And should I be concerned?

At around 1800-2000 rpm I hear this low frequency wobble sound. As if something is rotating but is not balanced.

I can only conclude a few things:

1) Not the engine as it's fine at idle and higher rpms
2) Not the tires/wheels as this happens on both track and daily sets
3) Not the dct as this happens in all gears, although I mostly hear it in 3rd/4th or 7th but I think that's purely coincidence.

Does anyone else hear this noise? Is this something I should be concerned about? It doesn't really bother me but I want to make sure something more severe isn't going on with my driveshaft or something.

Thanks.
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      08-13-2019, 01:49 PM   #2
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Quote:
Originally Posted by NYG View Post
At around 1800-2000 rpm I hear this low frequency wobble sound. As if something is rotating but is not balanced.

I can only conclude a few things:

1) Not the engine as it's fine at idle and higher rpms
2) Not the tires/wheels as this happens on both track and daily sets
3) Not the dct as this happens in all gears, although I mostly hear it in 3rd/4th or 7th but I think that's purely coincidence.

Does anyone else hear this noise? Is this something I should be concerned about? It doesn't really bother me but I want to make sure something more severe isn't going on with my driveshaft or something.

Thanks.
Is it during light throttle application and sounds like a putt, putt , putt type noise?
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      08-13-2019, 05:03 PM   #3
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Quote:
Originally Posted by drroc View Post
Is it during light throttle application and sounds like a putt, putt , putt type noise?
Yes, very light throttle so that it holds at around 2k rpm.

It's hard to phonetically type out the sound. This video is really close:



But without the high frequencies. Almost like you're rotating something on a string. No metal on metal noises. Just this wobble type sound.
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      08-13-2019, 06:08 PM   #4
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If you open your windows and drive close to a wall/divider at 20~30mph at 1800rpm and apply the throttle, you should hear that noise pretty well. So I am pretty sure it is an exhaust leak from the down pipe to the mid pipe. I am dealing with the same issue. I have loosened up the bolts and re-tightened them, and the noise went away. It is now back. So I'll have to get the gasket, and replace it.
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      08-13-2019, 10:58 PM   #5
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Quote:
Originally Posted by drroc View Post
If you open your windows and drive close to a wall/divider at 20~30mph at 1800rpm and apply the throttle, you should hear that noise pretty well. So I am pretty sure it is an exhaust leak from the down pipe to the mid pipe. I am dealing with the same issue. I have loosened up the bolts and re-tightened them, and the noise went away. It is now back. So I'll have to get the gasket, and replace it.
I'm not so sure this is the sound I'm hearing though. I'll look under my car tomorrow. When you're driving with your windows up and music off, do you hear that rotating sound I'm describing at like 2000 rpm?
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      08-14-2019, 01:42 AM   #6
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Quote:
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I'm not so sure this is the sound I'm hearing though. I'll look under my car tomorrow. When you're driving with your windows up and music off, do you hear that rotating sound I'm describing at like 2000 rpm?
There is no mechanical rattle like in the video. Its more like a pulsating sound during throttle application. Its most audible at slower speeds with windows rolled down. However, I am pretty sure it is from the downpipe to midpipe junction.
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      08-14-2019, 07:56 AM   #7
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Quote:
Originally Posted by drroc View Post
There is no mechanical rattle like in the video. Its more like a pulsating sound during throttle application. Its most audible at slower speeds with windows rolled down. However, I am pretty sure it is from the downpipe to midpipe junction.
So I'm hearing it with my windows up but I have a little less sound insulation in my CS. I want to lift the car and check this area. Would there be water coming out on a cold start in that area? Or would I have to have someone give it a few revs to see.
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      08-14-2019, 12:16 PM   #8
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Quote:
Originally Posted by NYG View Post
So I'm hearing it with my windows up but I have a little less sound insulation in my CS. I want to lift the car and check this area. Would there be water coming out on a cold start in that area? Or would I have to have someone give it a few revs to see.
Before I redid the bolts, I could also hear this noise quite well with the windows closed. Now, I need to open the windows to hear the noise. Yes, there should be a few droplets of water that come out from that area. You should be able to see them on the floor. Obviously, asking somebody to start the car when it is lifted and gently push the throttle a few times will help.
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      08-17-2019, 10:08 PM   #9
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Dealer says no leaks.
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      08-19-2019, 03:40 PM   #10
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Dealer says no leaks.
But I assume the noise is still present, right?
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      08-19-2019, 05:02 PM   #11
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Quote:
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But I assume the noise is still present, right?
As of right now, I had MP HAS installed, oil flush, rear diff fluid flush. I haven't heard it yet but I'll need a few days of driving to see.
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