308 QV Fuel Leak

One day after driving I found the garage and even the connected room in the house smelling strongly of fuel. Still does after 2 months. Not much smell when opening the engine lid though.
The fuel seems to slowly drop from somewhere around right fuel tank, as seen in picture. I don't find any fuel from the connecting pipe on top of the tank, so best guess is the outgoing pipe connecting back to the left tank. Considering the time it's been smelling, doesn't seem to stop until right thank is empty, which would also point at the a lower connection...I doubt the tank itself would leak??
Any ideas, or someone that experienced the same in 308/328?

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I don't see a photo, but you should be able to find the source if you get it up on a lift. All the suspect parts are visible. I will add that leaks from the aluminum tanks are rare but possible. The bottom of my left tank had to be reconstructed due to perforations caused by galvanic corrosion with the steel parts inside (outlet fittings, sender unit).

 

I don't see your picture, but you may want to check and see if the water pipe that runs in front of the engine has rubbed a small hole in the tank. If you do find some minor holes or pitting in your tank you can repair it with Proseal or similar product. It is used on aircraft fuel tanks.

 

There are many rubber hoses in the 308/328 fuel system (all those on top of the tanks) that only convey fuel vapors and not liquid fuel -- so, if they "leak", you won't see any evidence, but you will smell it. The original style rubber fuel lines that F used, with the reinforcement on the outside, are notorious for still looking good on the outside while the rubber inside is in dreadful condition. What version 308/328 do you have -- US, euro, euro modified for US, something else?

 

Well I had a leak on the right side like that and it was the fuel return hose that goes into the top of the right tank from the fuel distributor. It will leak when the car is running regardless of how low the fuel level is in the tank and it might not be so obvious because the leaking fuel just runs down the side of the tank and ends up dripping off the lowest point on the car it can get to.

 

+1 -- this is why 308i/308QV/328 Owners who don't DIY should at least learn how to unplug the blue-green safety switch on the airflow metering device and turn the key "on" to run the fuel pump (and pressurize things) without the engine running.

 

Common leak because that hose makes a 90 degree bend over the straight nipple on the tank. Because if that bend the nipple wears through the return hose. Had it happen on my car 10 years ago. Easy fix with wheel and finder liner removed. Low pressure hose is fine.

 

Don't rule out the tank leaking, my 83 started leaking in the sump on the left tank a couple of years ago. I went from no issue to full on leak in a matter of day's. The guy I had weld it said the original weld was bad probably from some kind of contamination when it was built. Not sure if the coating they put on it held it all these years or ? If you haven't already pulled the inner wheel well liner I would and see if there's any staining of obvious sign of leaking. After going through previous owners documents I found a receipt for a repair on the right tank as well. The fact that it stops leaking when the tank is low makes me suspect the tank.

 

Thanks for all fast and good answers and theories!
Unfortunately I don't have a lift but when putting my hand up above the wet area I can feel liquid where the mentioned water pipe is close to the fuel tank. There is no liquid on the same pipe further up, so I suspect that it may have rubbed a small hole in the tank as mentioned. I put the camera up and tried to get a picture. Seems to be a problem for me to add pictures...Let's see if it works this time Image Unavailable, Please Login Image Unavailable, Please Login

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I guess it will continue dripping until the right tank is empty. Hopefully not any danger driving to the service place since a few drops will just fall to the ground. I don't assume there would be any fuel pressure in the tank that would spray fuel upwards to the hot engine.

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FWIW, I had a gas smell (no visual drips or leaks) that we just couldn't track down, I was reading an old thread for whatever reason (Crowndog's Adventure 3.4) and I saw the below picture. Got me thinking. Sure enough, all the nuts on the top of the tank were loose. Might be worth taking a look.

 

That's the left tank.

Tip: for tracing the source rather than feeling use a clean blue shop towel to touch areas and see if it soaked up any fuel. The path it takes can be deceiving, it will flow just like a river the path of least resistance.

 

Although that's not false, I just want to make sure you're not under the impression that the two tanks are separate. They are one vessel, joined by a large pipe running between them. So the right tank is never empty unless you pull the plug in the bottom of the crossover pipe and empty everything. Also interesting that on the FI cars fuel is drawn from the left tank and returned to the right tank, so there a constant flow of fuel through the pipe in normal use. I mean aside from cornering, which very much transfers fuel from one side to the other.

 

Your big hose connecting the two tanks at the bottom is leaking.

 

Next strange thing....I pulled up the oil stick and it almost level is overfull, almost a decimeter over max and liquid pouring down from the stick. I know the level shouldn't be checked on cold engine but I never seen this before. Feels like a connection to the leak, but now I'm completely lost what's going on.

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False alarm...back to normal after engine start...


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You're most likely looking for something like this:

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Take care and get it fixed pronto.....

Best regards Peter