BMW X5 4.8is Strange Scratching/Grinding Noise from Fuel Tank Area - please help

[Lion Heart]

Hi guys!

Ok, so I have a high pitched electrical noise noticeable from standing outside the car next to the rear drivers side door especially. It was advised this was likely the fuel pump...

I managed to get the car on a ramp, went underneath with the engine running and the high pitched noise definitely seemed to be coming from the bottom of the fuel tank area. And it was also accompanied by a grinding/scratching kind of noise as well.

So, my thoughts get the fuel pump changed ASAP.

So fitted a brand new fuel pump (not too bad a job to do to be fair). The high pitched noise has now gone (hooray!) but that grinding/scratching noise is still there and does not sound very nice.

You do need to be close to the underside of the fuel tank to hear it, you cannot hear it inside or outside the car AT ALL unless you're within a few inches of the underside of the fuel tank.

I've taken a video and would really welcome some opinions on it...

https://www.dropbox.com/s/mk41qg13ana8w ... inding%20N oise.mp4?dl=0

You can hear it quite clearly grinding/scratching when I zoom in close to the bottom of the tank.

Now, that's a brand new fuel pump and it did this same noise before and after the pump change, so I would think it must be something else? Is this noise normal?????

[Alan Gunn]

Sounds like a bearing to me but very strange.

[Lion Heart]

Yes, kind of has a very slow turning bearing kind of sound I guess. Definitely sounds rotational, but not very quick.

Definitely only noticeable up close, but does not sound like a good sound!!!

[henrym3]

When you put the pump in did it fit perfect and have no distortion when secured

[Lion Heart]

The new pump fitted absolutely perfectly, as did the old one that was removed.

No warping etc to the frame, all seemed perfect.

I'm thinking unlikely that the noise is from the fuel pump as it's had two and the noise is still there. But unsure what else is in there (or near) that could make the noise???

[X5Sport]

Air suspension pump?  It’s under the spare wheel below the black dome in the boot.

[henrym3]

does the noise change with fuel level especially when full. Have you listened closely in the area of the sucking jet pump, noise can travel could be a crack in one of the pipes/plastic bits. Not sure of the top of my head how to but have you checked the fuel levels on the OBC for each side of the tank which might indicate there is a problem. Obviously have to get into the hidden menu to get that info.

[Lion Heart]

Hey X5 Sport. I have already stripped out the boot area as suspected the high pitch noise may be the susension pump, but no it was the fuel pump. So pretty sure it's not that. The scratching is definitely somewhere in the fuel tank region, and the suspension pump is a but further back I think...

Hey henrym3, not sure on fuel level TBH. I guess it's kind of lowish currently. I don't think the fuel light has come on yet though. Is there some kind of pump that transfers the fuel from one side into the main side (the one with the fuel pump ie offside), or is it a gravity thing?

Just trying to think what on earth could actually be making the noise?

[Smeeagain]

Why have you put up two separate posts on the forum about this?

[henrym3]

This is your system, if the fuel level is lowish it may be trying to suck it across and if one of those pipes are cracked and it's sucking air this may be what your hearing. Of course I could be talking bollocks.

[briankerrys47]

[quote="Smeeagain"]
Why have you put up two separate posts on the forum about this?
[/quote]I thought that,but was waiting for yooouuuuuuu  ) )