worrisome noise M5 mufflers on 550i

lamanite · 12-07-2018, 10:28 PM

I just had an exhaust shop put M5 mufflers on my 550i. Only mufflers got changed out. It sounds much better than the stock mufflers did but I've discovered a strange noise after accelerating and backing off the pedal. I can't tell if it's a burble or actually the exhaust flexing. It's like a bass thump in the trunk and the longer I drive (the hotter the mufflers get?), the more pronounced it becomes until I can actually feel it in the floorboards of the car. I can't seem to replicate it in park, the car has to be moving. It only happens when I mash the pedal and get up past 3K rpms and then let it decelerate. I hear/feel the noise on deceleration like it might be an exhaust burble. I can barely hear it in Comfort Mode for some reason. It's really pronounced in Sport mode. That might just be the higher rpms. I don't know that much about exhaust systems and I'm worried that this sound isn't normal and maybe the exhaust is flexing on a brace or something and causing the sound. Or maybe it's normal? Has anyone else ever experienced something like this?

335speed · 12-08-2018, 02:18 AM

I have m5 mufflers and wouldn't say I have experienced what you have described....

RMNB · 12-08-2018, 08:20 AM

Have your tech check it out to assure proper installation. Doesn't sound like it's loose but as the muffler heats up it may have shifted. I've experienced this on a couple of muffler installs and it was a fitment issue. A little bending and pulling worked especially when it rained. Rattled like crazy when it got soaking wet. Different situation but might point you in the right direction.

lamanite · 12-08-2018, 02:37 PM

So I had a different shop check it out today and they say everything is tight. They suspect it's something in the a muffler like a blown baffle. Not sure where to go from here. I'm doing research on what could make a muffler make bumping noises internally. I'm only finding info about rattling

335socal · 12-14-2018, 12:30 AM

Quote:

Originally Posted by lamanite

So I had a different shop check it out today and they say everything is tight. They suspect it's something in the a muffler like a blown baffle. Not sure where to go from here. I'm doing research on what could make a muffler make bumping noises internally. I'm only finding info about rattling

Check if the muffler is touching any of the heat shields.

tufarella · 12-27-2018, 01:48 PM

Did you ever find out what was wrong?

12-07-2018, 10:28 PM	#1
lamanite New Member 0 Rep 18 Posts Drives: 2014 550xi Join Date: Sep 2018 Location: Seattle iTrader: (0)	worrisome noise M5 mufflers on 550i I just had an exhaust shop put M5 mufflers on my 550i. Only mufflers got changed out. It sounds much better than the stock mufflers did but I've discovered a strange noise after accelerating and backing off the pedal. I can't tell if it's a burble or actually the exhaust flexing. It's like a bass thump in the trunk and the longer I drive (the hotter the mufflers get?), the more pronounced it becomes until I can actually feel it in the floorboards of the car. I can't seem to replicate it in park, the car has to be moving. It only happens when I mash the pedal and get up past 3K rpms and then let it decelerate. I hear/feel the noise on deceleration like it might be an exhaust burble. I can barely hear it in Comfort Mode for some reason. It's really pronounced in Sport mode. That might just be the higher rpms. I don't know that much about exhaust systems and I'm worried that this sound isn't normal and maybe the exhaust is flexing on a brace or something and causing the sound. Or maybe it's normal? Has anyone else ever experienced something like this?
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12-08-2018, 02:18 AM	#2
335speed Private First Class 12 Rep 193 Posts Drives: 16 550 Join Date: May 2013 Location: SoCal iTrader: (0) Garage List 2007 BMW E90 [10.00]	I have m5 mufflers and wouldn't say I have experienced what you have described....
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12-08-2018, 08:20 AM	#3
RMNB Lieutenant Colonel 365 Rep 1,649 Posts Drives: 2021 440xi CPE BSM Join Date: Jul 2013 Location: Maryland iTrader: (0)	Have your tech check it out to assure proper installation. Doesn't sound like it's loose but as the muffler heats up it may have shifted. I've experienced this on a couple of muffler installs and it was a fitment issue. A little bending and pulling worked especially when it rained. Rattled like crazy when it got soaking wet. Different situation but might point you in the right direction.
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12-08-2018, 02:37 PM	#4
lamanite New Member 0 Rep 18 Posts Drives: 2014 550xi Join Date: Sep 2018 Location: Seattle iTrader: (0)	So I had a different shop check it out today and they say everything is tight. They suspect it's something in the a muffler like a blown baffle. Not sure where to go from here. I'm doing research on what could make a muffler make bumping noises internally. I'm only finding info about rattling
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12-27-2018, 01:48 PM	#6
tufarella Registered 0 Rep 2 Posts Drives: 2011 BMW 550i xdrive Join Date: Dec 2018 Location: Cincinnati iTrader: (0) Garage List 2011 BMW 550i [0.00]	Did you ever find out what was wrong?
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