So it's almost a year since I got my 335i, & for the most part I would only partially fill the fuel tank, because why cart more gas than needed.
However on the few occasions that I did fill the tank, I would notice a very strong raw petrol smell until the fuel level got down to 1/2 tank or below.
Read a couple of things that indicated an issue with the carbon canister in the venting, priced replacement & thought f**k that, & carried on regardless.
Then one day after filling the tank, I parked the car across a slope, with the drivers side down hill.
As I got out of the car I saw petrol dripping from just in front of the right rear wheel. After getting over the shock, I turned the car round so it was across the slope the other way & once I was happy that there was no more fuel running out, went about my business for the day.
Started digging & found that there have been a number of the E90 series cars with this issue, & it appears that the breather hose that runs from the top of the tank to the neck of the fuel filler could be damaged due to excessive movement of the tank.
So, last week was a quiet week for work, & I finally got the chance to get under the car & repair the issue. I had bought a replacement vent hose, & expected that it would be a fairly simple, if somewhat laborious, task, to lower the fuel tank sufficiently to get to the breather hose & replace it.
More fool me!
When I got to that point, I discovered that the breather spigot that the vent hose clips onto had broken out of the fuel tank completely!
This then necessitated the complete removal of the fuel tank.
For those who have not had the pleasure, this requires removing the driveshaft & the handbrake cables (I had already removed the exhaust system) & this is where the fun starts.
To remove the driveshaft requires a 50mm open-end spanner & lots of brute force to undo the coupling point with the diff.
To remove the handbrake cables, requires gutting out & removing the entire centre console!
Once I had the tank out & could see the damage, I called BMW for a price. $1530+GST, & special order from Germany! Further explicatives followed for some strange reason!
Fortunately, many years ago I had sold some fellow car enthusiasts a tig welder, & they happen to run a company Plastics Constructions, in Avondale. I gave Richard a call, "can you weld a plastic fuel tank?". He checked the material, & "yes no problem" was his reply. He made a beaut job of it, & it's now probably stronger than the original.
So, if you notice strong fuel smells when you fill the tank, this may be something to watch for. Another check I would suggest, is to lift the rear of the car when the tank is empty, & make sure that the tank is tightly held by the securing straps. I was able to move my tank up & down by more than 10mm when I got underneath, & I have fixed this by putting thicker heavier foam blocks between the tank & the bodywork when I reinstalled the tank.
I still need to finish reassembly of the interior & final bolt-up of the exhaust, but at least my car won't leak petrol any more.
I will post some photos of the process & what to look for when I get the job completed