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      11-13-2017, 07:23 AM   #45
Walt White Coupe
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So here's a thread about exhaust 'rattle':

http://f30.bimmerpost.com/forums/sho...d.php?t=972489

As I looked through posts about the flappers there is sure a lot of confusion about what the flappers are for.

They are for increased horsepower at higher engine speeds.

I'm not sure what RPM they are programed to 'open' but the Corvette has a similar system that is called a 'Dual Mode Exhaust'. On the Vette the 'flappers' open at 3500 RPM and provide an extra 5 HP. As the power and RPM increase obviously the airflow through the system increases as does back pressure. Opening the valves at high power, reduces back pressure and increases HP because in the open mode the exhaust has a direct path through the muffler without going through the baffles and also increases the sound level.
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      12-31-2017, 02:36 PM   #46
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Well forget my post #43 about the "rattle" possibly coming from the exhaust "flappers".

I recently zip tied mine open to see how it would sound and the rattle was there in all it's glory on a 32 degree morning.

But another data point. The East Coast has been suffering through a very cold snap for the past week or so. So it's 15 degrees F and I go out for a ride. Absolutely no rattle. It was a short ride to the store. Back in the car that is now only slightly warm and the rattle is back in full.

I've been out now on a few sub 20 degree days and no rattle detected.

So it seems that the rattle only occurs in a rather narrow temperature band. From my experience it seems that the strong rattle will occur only between 25 and 35 degrees on a cold car. And will be a very weak rattle between 35 and 50 degrees.

The mystery continues.
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      01-02-2020, 07:34 AM   #47
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Walt,

Reviving an old thread. Your post #18 recording is exactly the sound mine makes, with the exact same symptoms. Your description is like you were driving my car.

Curious if you have just ignored the problem or if you finally figured it out.

L
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      01-02-2020, 07:56 AM   #48
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I've had no luck resolving the issue and now on cold mornings I just turn up the radio and try to ignore the rattle. Whatever is causing it can't be much of a problem.
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      01-02-2020, 11:07 AM   #49
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Same noise (from #18) here in Munich on cold mornings. I can definitely say that it is not coming from the (all) control arms, the strut bearings, or the output shafts, as all this parts were already exchanged in the last years due to other problems.

Actually I suspect the dynamic dampers due to the cold oil inside. It is more or less a comfort problem or "Serienstand" (--> current model version) would BMW say here
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      01-02-2020, 01:14 PM   #50
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Quote:
Originally Posted by Walt White Coupe View Post
I've had no luck resolving the issue and now on cold mornings I just turn up the radio and try to ignore the rattle. Whatever is causing it can't be much of a problem.
Thank you for the update Walt.

I just bought this rig in August 2019. Plan on keeping it for a while, so I want to get this resolved. As mentioned earlier, a $100,000+ car should not be doing this. I drove it this morning, had my phone ready to record it, but it did not produce the sounds. It was 48 degrees F, so perhaps not cool enough to cause the issue. I will continue to monitor and report back if I make any progress.

L
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      01-02-2020, 01:18 PM   #51
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Quote:
Originally Posted by Munich_Simon View Post
Same noise (from #18) here in Munich on cold mornings. I can definitely say that it is not coming from the (all) control arms, the strut bearings, or the output shafts, as all this parts were already exchanged in the last years due to other problems.

Actually I suspect the dynamic dampers due to the cold oil inside. It is more or less a comfort problem or "Serienstand" (--> current model version) would BMW say here

It would be great if a microphone could be strapped to the dampers. Drive it and record it. That would probably be pretty conclusive if it where the dampers or not. Actually might have found a good use for my old iphone 4s....

L
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      01-02-2020, 02:11 PM   #52
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Quote:
Originally Posted by Luftpost View Post
Thank you for the update Walt.

I just bought this rig in August 2019. Plan on keeping it for a while, so I want to get this resolved. As mentioned earlier, a $100,000+ car should not be doing this. I drove it this morning, had my phone ready to record it, but it did not produce the sounds. It was 48 degrees F, so perhaps not cool enough to cause the issue. I will continue to monitor and report back if I make any progress.

L
I agree 100%. I tried a couple times at the dealer by leaving the car overnight in winter but could never get it to duplicate the rattling noise so the service guy could hear it. They checked the complete front end suspension and even changed the front sway bar bushings but to no avail. Hope you have better luck determining what the cause is.
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      01-02-2020, 03:56 PM   #53
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Well, I decided to take it to the dealer. I'm at 50,600 miles, with 6 months left on the factory warranty, and then the CPO kicks in. I played Walt's recording to the SA (and emailed him the dropbox link which he asked for), and informed him that this was not my car, but another 650, and that it is a known issue amongst the 650 community. He heard it and is going to look into it. They are keeping the car for a few days. Temps will be in the upper 20's over the next few evenings, so they should be able to hear it. Had them look into some other things as well (passenger seat rattle with recording) as well as some minor other things.

My loaner is a 2020 530. It drives nice, but the quality just is not there like it is in the 650!

L
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      01-03-2020, 09:24 PM   #54
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Got the call from me dealer. Unable to duplicate the noise. He told me that if I get an audio of it from my car, they can check into it some more.

Frustrating, but I will do my own recording, and then check back with my SA.

L
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      01-04-2020, 12:03 AM   #55
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^^^
Sounds very similar and why I eventually just gave up as have others on this tread.

Hope you keep with it. But because the rattle goes away once the engine heats up, it's almost impossible to troubleshoot where it's coming from even if they do hear it with the engine cold.

When I had the SA in the car, I played the recording of the rattle through the car's audio system. Then I drove the car with him and once you know what you are looking for, you can hear the rattle even when it's very faint but he couldn't hear it. Like you said, frustrating.

Last edited by Walt White Coupe; 01-04-2020 at 12:09 AM..
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      01-04-2020, 11:48 AM   #56
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My car has the same rattle when its below 0 Celsius. On the bright side the front suspension squeeking is gone when its cold

According to my SA this is off course completely normal And yes my car have variable damper controle.
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      01-09-2020, 07:08 AM   #57
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I'm new to the forum. Apparently I need to post a reply before my account is upgraded. I've dealt with my fair share of rattles. I used sticky foam-board between plastic components in the cabin. Unreal that I had to do so in a new 640ix. I blamed it on the ultra harsh ride from the run flats. Not much better after I replaced them without improvement. Only to find out that the transport suspension blocks had been left in. Finally experienced a BMW ride 9k miles after taking delivery. More to follow on that when i get the ability to post.
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      04-15-2020, 08:07 PM   #58
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At the dealer revisiting this issue..........

I think we are making progress.

L
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      04-15-2020, 08:45 PM   #59
Walt White Coupe
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I hope so. I've pretty much given up. Would be nice if you solved this mystery.
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      04-21-2020, 07:22 AM   #60
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Last week, took my car to the dealer, after I made another recording demonstrating the noise. Went for a drive with the tech, just around the lot and immediate area. He heard the noise. They kept the car and called me the next day. It needs a new front right strut. Actually there was a lot more discussed at the time, but that is a whole other matter.

Picked up my car yesterday from dealer, after they had it for 5 days. I did not hear any noise. When I look through the Maintenance paperwork, it clearly indicates that they checked for loose body and suspension parts, but found none. Then drove the car with "Chassis Ears", and were able to isolate to the front right strut.

I must say the dealer was good to work with through this project. In particular the Service Manager. He called me directly last week for us to discuss the issue.

Hoping this is solved, and will report back if anything changes.

L
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      04-21-2020, 08:40 AM   #61
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I only have the rattle when it's cold outside (20 to 30 degrees F). And after the car warms up, it goes away. Did you have the rattling even when it was warm outside? Do you have the part number of what they actually changed?
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      04-21-2020, 09:38 AM   #62
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Last week, when I brought it to BMW, it was 46 degrees F outside, and the noise was present. This morning it was 50 degrees, and I took it for a short drive. No rattle.

P/N 313510 Spring Strut

I will continue to monitor.

L
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      04-21-2020, 09:54 AM   #63
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Thanks. Before the replacement and on a cold day, did your rattle go away when the car warmed up?
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      04-21-2020, 11:02 AM   #64
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Quote:
Originally Posted by Walt White Coupe View Post
Thanks. Before the replacement and on a cold day, did your rattle go away when the car warmed up?
Yes it did. Same exact sound as the recording that you edited.


Here is the note from the technician:

Verified Customer concern. Put vehicle in air and checked for loose or damaged component, found no damaged parts. Body panel for passenger side was missing body clip and replaced, test drove vehicle and noise was still present, checked tightness of suspension bolts and found ok. Test drove vehicle multiple times with Chassis Ears in different locations and found front right strut was making the same noise as heard when vehicle is cold and could still be heard via Chassis Ears when warmer. After repair, noise no longer heard.

L

Last edited by Luftpost; 04-21-2020 at 11:17 AM.. Reason: Added tech note.
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      04-21-2020, 11:41 AM   #65
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^^^^

Thanks for all that information. Did the service guy say anything about what in the strut was causing the noise like a loose bolt, broken something, etc or if whatever it was any danger to the integrity of the right suspension. I guess I'm asking if I should be worried about whatever it was? Can I just live with it since my car is way out of warranty?
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      04-21-2020, 02:04 PM   #66
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Walt,

I think these days, parts are replaced rather than diagnosed and fixed. Everything has become modular. There was no mention of what caused the strut to become defective. I do not believe that it was something obvious or visually identifiable. If I sent an email to the service advisor, I am sure she would respond back “strut defective”, with no explanation, nor do I think that the tech really cared. They just move on to the next job.

I am aware that others on this forum, from all over, have had this same issue, so I do not think it is isolated. Perhaps there was a batch that went out, that had a defect in them, and later corrected on the next production run. Who knows.

This kind of stuff really interests me. Last week I did a bunch of digging online to understand how this stuff works. There is one particular YouTube channel “Engineering Explained” that has a great video on how these things work. Then I looked up Brownian Motion.

https://youtu.be/hiaMpG4Y640

I have always felt that it is better to be informed than uniformed, that way there is less of a chance you will be taken advantage of. This knowledge did in fact come in handy when I was talking to the service manager.

Anyway, the part costs roughly $300. There is another thread on this site by Board57796. He created an incredible DIY on installing lowering springs. This thread would be a good tool if you chose to do the job yourself. I was able to get it done at a significantly reduced rate (BMW Goodwill), had that not been the case, I would have had my Indy do it.

https://www.6post.com/forums/showthread.php?t=1553730

L
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