BMW 3 Series 335i manual 2012 50k miles - Annoying noise

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Sun 21 Jun 2020 17:08
BMW 3 Series 335i manual 2012 50k miles - Annoying noise - Kevin Remmington

Please can someone identify this annoying scrapping / rubbing noise. It starts at about 30mph in any gear : dosn't change volume or pitch : happens on most journeys : can't hear above 50mph : happens even it coasting : dosn't change with speed, braking or cornering or applying handbrake : appears to be behind the driver : stops abruptly below 25mph ! : have checked under floor panels, exhaust fittings, heat sheilds, body panels, rear seats, boot luggage : owned car since new ; serviced regularly ; started end of 2019

I'm baffled

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Sun 21 Jun 2020 20:37
BMW 3 Series 335i manual 2012 50k miles - Annoying noise - gordonbennet

I'm baffled

You might have answered your own question there in a way.

Possibly something like an underbody plastic cover that either vibrates or rubs against something on the body itself above 25mph.

You might see it if you get the car up in the air, and it might be visible should you get someone to drive your car at that speed on a quiet road whilst you follow and observe from all angles what is happening...not particularly BMW's but i often see VW Golfs with the engine undercover being pulled down to nearly touching the road when the wind catches them, possible something similar is happening here?

Have you checked the propshaft, and driveshafts, something catching those?

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Sun 21 Jun 2020 22:55
BMW 3 Series 335i manual 2012 50k miles - Annoying noise - Kevin Remmington
Thks for replying

Have had the car on ramps many times to check the under panels. There appears nothing to cause such, and that includes the heat shielding panels. The prop isn’t visible for most of its length, but my logic is that that would change the pitch due to different rotating speeds. So what starts at about 30mph and stops abruptly under 25mph. As you state could be wind speed related. One possibility is the fuel check valve, but don’t know how to start investigating. The noise level does change with the rear seats down, but could be just easier for the sound to travel. Could be the fuel tank, but it doesn’t alter with full verses empty. Still baffled !
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