Whining sound as if wind is going through a pipe comping from the fuel tank
I have a very strange and annoying problem with my 2001 740I BMW. A whining, intermittent sound coming from the driver side of the fuel tank. It sounds a bit like whistle of wind going through a pipe. I thought it was the fuel pump, so I replaced it but to no effect. The Bentley manual mentions that there is a siphon pump to equalize the levels in the two lobes of the tank. I suspect this might be the problem, especially because it sounds like a noise produced by the turbulent flow of a fluid. I could not find anyone selling a pump like that. It looks like it is part of the fuel tank. Does any one know on what principle this pump operates and if I can see it if I remove the fuel pump or the fuel level sensor? I guess this is not an electric pump. Has anyone had any similar experience? Thank you very much.