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Discussion Starter · #1 · (Edited)
Not only am I dealing with this:

http://www.m5board.com/vbulletin/e6...ussion/157416-intermittent-buzzing-noise.html

which is an internal sound while driving... but I'm also dealing with these exterior noises after going on an hour long drive and then parking and shutting the engine off:

a.) Metal on metal grating noise

No clip of this one yet. Doesn't happen often and doesn't last long enough to grab a camera to record. This is with the engine off and car turned off and no one in the car. It sounds like a soft metal on metal grinding sound. Comes from near the front brakes. I think it's coming from the thin metal shield behind the brake rotors. It actually sounds similar to when you run your hand on that shield (while it's cool of course -- don't burn your fingers). Is this a normal sound from that shield cooling after a long drive?

b.) Some compressor sound and pop in the rear end

I heard this one for the first time today. Got out of the car after the hour long drive and heard what sounded like an air compressor or fan spinning. Thought it was the front fan so I checked there and no, that wasn't it. Went to the rear end of the car and it was louder there. Got up close next to my rear wheel and you can definitely hear it. I started recording a video below (note again, this is with the car off!). It's not the crackling noises -- that's my exhaust cooling. It's the air compressor/fan noise in the background. And then around the 1:07 mark, you hear this loud POP and then the sound is gone. WTF? What is that?

 

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Discussion Starter · #4 ·
Appreciate the responses as that sets my mind at ease but where exactly are those noises being generated from? A mechanical explanation would be great as I am curious as I have never heard my car make those noises before.
 

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Discussion Starter · #5 ·
Went into the dealer today and played the clip for them of sound B) above. They had no idea what it was. They think the compressor-like hum sound is from the SMG pump. And they said it would be normal for that to kick in like that after spirited driving and after I turn the engine off as it wants to keep the pressure steady while the car cools down. But they were scratching their heads on what that pop sound could be and why the SMG pump sound would stop at that point. They think it might have been coincidence that the two events happened at the same time. They think the pop sound might be a cat pop? Anyone know what that is? I'm guessing something to do with the cats but that's the first I have heard of it.

As for sound A) they have no idea. I don't have a recording so I couldn't play it for them so I guess I still need to keep my video camera handy. At this rate I should just buy a Flip camera just to keep in my car.
 

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I have had the exact same noise minus the pop. Mine comes mostly from my passenger rear side (almost like it is coming from the behind the wheel) and only after some spirited driving right before I turn it off. I have heard it several times. I have an 08 with 40,567 miles.
 

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Discussion Starter · #7 ·
Yeah, same location for me. Behind the right rear wheel. That's where the video above was taken. I can handle the compressor noise (if that's normal SMG pump noises -- although it does not sound like the SMG noise when you first unlock the car). But the pop is the thing that bothers me.
 

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Discussion Starter · #8 ·
I played the sound to a mechanic at a local independent BMW shop (mechanics are ex-dealership folks). He said the E60 M5s have some engine optimization? features that run for a few minutes after the car is shut off that burns off extraneous fuel for emissions purposes? He thinks the pop is from that and completely normal. Also says that the pop has an echo to it which suggests its coming through the exhaust tubes and further validates that theory. Only theory I have heard so far. Hope it's right.
 

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theres a small cooling system in the trunk on the right side to cool the electronics and sometimes makes load noises. opent he trunk and see if its loader
 

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Went into the dealer today and played the clip for them of sound B) above. They had no idea what it was. They think the compressor-like hum sound is from the SMG pump. And they said it would be normal for that to kick in like that after spirited driving and after I turn the engine off as it wants to keep the pressure steady while the car cools down. But they were scratching their heads on what that pop sound could be and why the SMG pump sound would stop at that point. They think it might have been coincidence that the two events happened at the same time. They think the pop sound might be a cat pop? Anyone know what that is? I'm guessing something to do with the cats but that's the first I have heard of it.

As for sound A) they have no idea. I don't have a recording so I couldn't play it for them so I guess I still need to keep my video camera handy. At this rate I should just buy a Flip camera just to keep in my car.

Well, I have a 6-speed and mine makes that noise, so it can't be the SMG. Sounds like an air pump running and then the pop is the pressure shut off, just like my shop air compressor. I have listened to it around the car in my garage and it seems to be coming from the rear somewhere. I opened the trunk but it seemed to be coming from under the car, not inside the trunk.

It concerns me when I have to leave the car with stuff still running. The cooling fan, this pump, and who knows what else. I always worry if it will shut off or not, and not leave me stranded due to a weak battery. But so far it's been okay after a year, so I guess it's fine. I still don't like it, however.
 

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Sorry to resurrect an old thread, but B is exactly what I'm experiencing and I'm very interested to know what it is. I have not stuck around long enough to hear any popping sounds, but I have heard this weird compressor sound coming from my rear passenger side wheel well after turning the car off.


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you sure it's not the SMG pump priming?
 

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My understanding is that the SMG pump sound comes from under the hood and happens when I unlock the car (for instance). If that is right, I know THAT sound well, and it is not the same as the one described in this thread.


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