High pitched hum from rear.....?

[KenSmith]

2006 Z4 3.0si....I get a high pitched humming noise coming from the rear of the car I think while driving. It seems to only happen when the gas tank is under 1/2 full. Could this be the fuel pump? If so, is it ready to go out? Or is this normal which I doubt. Car has 51,000 miles. Thanks!!!!

 

[stupot67]

Hi Ken,

Same here, albeit only barely noticeable at very low speed (I.E parking etc) and not at all when the tank is full - If it was the hi pressure pump fitted to the direct injected engines (Some E89's) it might be of concern.

But for ours, I wouldn't worry unless it's really LOUD! - After all your sitting only about six inches above the pump so any noise is going to be noticeable.

Stu.

 

[KenSmith]

Ok, thanks. Prior owner said he never noticed it but I heard it when it got below 1/2 tank. At 1/4 tank it seems to be a little louder. (with radio off). I hear it while driving even with the top down.