Wet fuel tank?

[CSN327]

Hi guys,

I got my E85 Z4M on the lift , and found the fuel tank looked wet.







Does it look bad?
Is there any way I can figure out this without taking the tank out (and replace it with another one?)
It seems that I can’t top over 14 gals (maybe will verify this on another day, but I think it definitely had some margin to 14.5 gal) and I get 18 mpg on avg speed 30mph with top down.

I think it most likely hit something on the passenger rear as the control arm is bent.



Looking forward to your advices!

Thanks,
CSN327

[Our03z4]

I remember seeing someone post about this same thing. If I remember right it was something to do with the fuel pump leaking on top. Feel like it's also a huge pain to get the tank out. Could be damage on the tank from that hit or it could be the other. Good luck!

[grannyknot]

I removed my entire drive line last winter and I saw the same thing, same amount of stain. I remember thinking at the time that it was grease sling from the U joint on the driveshaft but it might be some seeping from the fuel pump gasket.
But if that is all there is to show for 15 yrs of driving then I don't think it is a serious issue.
I just cleaned it up with solvent.

[CSN327]

When I pull off on the pump I’m pretty sure it is on the fumes (range 2mi). I can only put 13.5 gals to the tank. After the third try to pump more I noticed there might be overfilling on the gas cap. Is it concerning that I just can’t fill the last gallon? Is that a symptom of a leaking fuel pump? Thanks!

[Our03z4]

Never try to keep filling the tank, you'll ruin the evap system. Most I'm ever able to put in mine is around 12-13 gals.

[GuidoK]

Originally Posted by CSN327

Is that a symptom of a leaking fuel pump? Thanks!

I don't think this is gasoline.
If your tank is this wet with gasoline, it'll reak immensely and it probably would be actively dripping on the floor as it is very evaporative. (I see wetness on a control arm, that would not be likely if it was gasoline).

I think it's oil, probably coming from a leaky front input shaft diff seal, looking at the location (known z4m problem)

Or do you smell lots of gasoline?