Quote:
Originally Posted by cruisn76
My first post here, and I have the same knocking sound on my F36. I notice it closer to 1/8 to empty and I can get rid of the sound by simple opening the gas cap. I believe the fuel pump is partially submerged under fuel at 1/8 and the noise is amplified. But once I pop the gas lid, it releases the pressure and the knocking sound instantly disappears
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Quote:
Originally Posted by cruisn76
My first post here, and I have the same knocking sound on my F36. I notice it closer to 1/8 to empty and I can get rid of the sound by simple opening the gas cap. I believe the fuel pump is partially submerged under fuel at 1/8 and the noise is amplified. But once I pop the gas lid, it releases the pressure and the knocking sound instantly disappears
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Wow! I totally forgot about this thread and am glad that folks are chiming in again.
You are actually pretty correct about the cause of the issue. I had my first oil change with my dealer a few months back and mentioned this issue and the shop foreman was very upfront and told me basically that it had to do with the fuel pump venting system so it is an emissions related issue. BMW is fully aware of this issue and has no fix as of a few months ago but they thought that they could update the software eventually which would "pulse" the venting at such a rate that it would essentially mask the noise. So yes. It was indeed a design flaw that should have been caught. My 2015 335ix didn't have this issue so they somehow "engineered" it in due to poor testing.
Like some here, I can hear it below 1/8 tank full. It can start as early as 1/2 tank as well but only for a short while if I brake hard and the gas sloshes around and causes the fuel pump to not be fully submerged. But I will honestly say that the noise is of a lower intensity now vs when i first picked up my car.
So it's a wait and see game. I filled out one of their BMW post service surveys and told them that they need to find a fix soon in their "what would you like BMW to know" section. I will definitely post an update if I hear of anything. I will mention this again this year when I go in for my 2nd service.