W639 Vito/Viano - small amount of fuel dripping off bottom of tank.

[BTB 500]

Noticed a small circle of fluid under the Vito today roughly below the fuel filler - from a quick inspection this proved to be diesel. The tank is about half full and the vehicle hasn't moved for 4 days. Looking underneath there's a plastic pipe with an open end near the top of the tank. It looks like this is where a small amount of fuel has been dribbling from ... this is after I wiped the U bend of the pipe:





This pipe is thin-walled and quite large bore. It's fairly rigid ... the open end doesn't feel like it has broken off, and I couldn't feel anything on the top of the tank that it might have come away from. It's not possible to see in there (I did think afterwards that I might be able to with an inspection mirror).

Could it be a breather of some sort? There's no drain in the fuel filler compartment as you get in some cars, so it's not that. If it goes to the tank the open end can't be right as road spray would potentially get in when driving in the wet. The vehicle is always parked on the smooth concrete floor of our barn and the relatively small amount of fluid was immediately obvious when walking past ... I've never seen (or smelled) it before. The tank itself is plastic AFAIK.

Any ideas?

 

[m80]

I thought we did have an overflow / vent at the filler. But I've just checked and there isn't, so my memory isn't of much value it seems.

FG 639.815 - FUEL TANK VENTILATION > Mercedes EPC Online > nemigaparts.com

Parts catalogs. Spare parts catalog Mercedes EPC Online. Mercedes. Van. FUEL TANK VENTILATION.

nemigaparts.com

Would the pipe be 80 in the diagram?
Would that indicate a blocked filter at 180?

 

[BTB 500]

I thought we did have an overflow / vent at the filler. But I've just checked and there isn't, so my memory isn't of much value it seems.

FG 639.815 - FUEL TANK VENTILATION > Mercedes EPC Online > nemigaparts.com

Parts catalogs. Spare parts catalog Mercedes EPC Online. Mercedes. Van. FUEL TANK VENTILATION.

nemigaparts.com

Would the pipe be 80 in the diagram?
Would that indicate a blocked filter at 180?

That sounds/looks feasible ... or could possibly be an issue with that purge/regeneration valve, which I assume the tank vents through? I notice that has been replaced with a different part number.

I wonder where the filter is physically located ... should be somewhere accessible, unlike the valve I suspect!

Many thanks for your advice, and have a great Xmas!

 

[m80]

I seem to remember a canister, that is likely a / the filter, inline on pipework, underside.

But I have used my Viano as the reference to look at the Nemiga drawings, it's possible yours could vary some

I hope you enjoy your day festive season also.
I'm looking forward to taking Mishka walkies soon, that'll be a pleasure. I'm sure many of the family wishing to tag a long will be nice, although it's very muddy round here. My boots will be fine, not sure about their high fashion shoes.

 

[Michael4012]

Interesting thread, I am having the same issue with a 2014 116cdi, however the MOT inspector failed it quoting "fuel tank leak" which it isn't. I have never seen a fuel puddle underneath or smelt fuel. Has there been an update to this? Is that where I go replace the filter?

 

[BTB 500]

Not much help I'm afraid but after over a year now mine hasn't done this again!

 

[Michael4012]

Thank you, yes I cleaned it all up and totalled 80 miles last night and it hasn't happened again. I'm taking it back in today it's obviously not leaking so it should be a pass.

 

[Michael4012]

It appears to be the vent from the tank, there is no vent on the filler pipe so this is responsible for excessive pressure, I can't say it's particularly warm or cold this time of year but I had been I the habit of brimming when I fill up. You can see the pipe on this tank listed for sale on flee/bay