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      01-20-2021, 10:55 AM   #10
Boston4
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Drives: '11 E90 N51 M-Sport 6MT
Join Date: Dec 2020
Location: Boston, MA

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Quote:
Originally Posted by Boston4 View Post
I had this happen this past weekend on a trip with my E90 - the weather was cold, but I think that I've isolated the issue to a different factor: water.

Was it raining when this happened to you? I'm thinking I have some kind of exhaust leak that presents itself when driving in moderate-heavy rain. The issue was definitely present through an hour of back roads to get to my destination in the rain. I parked for about 20 minutes and it disappeared when I started it back up, until I got back on the main road - at that point, water and loud exhaust returned.

I drove home 3.5 hours in dry conditions with normal volume levels in similarly cold temperatures. Not quite sure what to make of it.
Update: This issue is caused by a very minor exhaust gasket leak. The bolts are just rusted out and it won't hold a seal - the issue is exacerbated by water causing the metal to contract and lose the seal. Interestingly, it doesn't sound bad even during cold starts - only happens when driving in the wet.
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