fuel leak

[basespec1series]

Hey BMW Fanatics

Relatively newbie here coming for some help.
A few months ago when I filled up my F20 116i full tank, I noticed a slight fuel smell.
I immediately left for a long road trip and wrote off the problem as probably just residual fuel/carelessness at the garage.

Since then I always just filled 1/2 or 3/4 tank and never experienced the problem again.
Recently however, I needed a full tank and filled it up -up to 1st click. The fuel smell came about again, but alas, after driving 100-200km, and fuel level went down, so did the smell (not giving me a chance to see what the problem is). I inspected under and everything looked fine.

So I refilled again and let the car stand for a day, and now the problem is clear. The rear end of the fuel tank is wet, with amount of minor leaking (probably dripped about 20-30ml of fuel overnight).

Has anyone experienced this before?

I'm sending it through to my trusted mechanic tomorrow/Monday and it is suspected to be a fuel tank leak.
The kicker? BMW SA quoted R17k incl. for a new tank

Other suspected causes are worn O-Rings, cracked fuel pump, maybe a gasket(?)

 

[Jive_E46]

Get another fuel tank from the scrapyard. Just test for leaks.

There’s plenty front smash F20’s waiting for their fuel tanks to be pulled out.

Good luck!


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[basespec1series]

Thanks, @Danny2 managed to sort me out! - Shout-out to Danny, always willing to take time to thoroughly diagnose and sort issues out

The fuel leak issue seems like it's a common F20/F30 issue -

The tank is re-purposed from other models, with the gap for the fuel regulator covered up with a cap, and over time the seal around the cap weakens, causing fuel to leak out but only when it's full to the brim...

 

[Holiman]

This is actually awesome. My car is on for anew fuel pump Soni am wondering if this is worth checking and doing while the car is in.

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[basespec1series]

It depends - I think the fuel pump is relatively easy to change as it's under the seat.

Covering up the seal is quite labour intensive as they'd need to drop the tank

 

[basespec1series]

Update on this for anyone who comes across this issue. About a year after the fix, I ended up having to repalce the tank alltogether as fuel naturally eats up any sealant/fix that you put over the part of the tank that leaks.