|
Definitely not cats cooling or any garbage like that. I would venture a guess that it's an echo chamber effect in the near empty tank, or even more likely the fuel pump struggling to pump the lower level of fuel in the tank. Perhaps a mix of both, where the fuel pump is more easily heard in a near empty tank versus submerged in fuel. The consistency in the thumps make me believe it's a mechanical noise, hence the fuel pump. Since it seems common I wouldn't worry, but the E90/92 had poor fuel pumps so it's not necessarily shocking that BMW beefed up the units, maybe making it noisier?
|