2008 C5 Hdi - fuel tank leak when filled

[rdodger]

Hi, I have twice filled the tank to near full and each time there has been diesel leaking afterwards , seemingly near the top. However my mechanics cannot find the source but will change the seal on the sender unit as a 1st step though it’s not apparent to be coming from it. Anyone experienced this before?. We’d much appreciate any pointer. Thanks. Roger

[GiveMeABreak]

Don't fill it past the third click - but this does need thorough investigation obviously. There should also be a fuel filler gasket towards the top of the filler pipe.

[wheeler]

If It was leaking from the fuel sender seal it would be really obvious as there is a 'well' around the base of it where all the fuel would gather. It's also quite unusual for this seal to fail unless it has been recently disturbed. Any work been done on the fuel tank? If you do need to get the seal replaced make sure the fuel tank is less than quarter full before removing the plastic ring, if there is too much fuel in the tank plastic fuel tanks can (and do) distort & you can't get the ring back on again, even after draining the tank.

[rdodger]

Apologies for the late follow up reply. A year on I still have the same issue but just don’t fill the tank over 3/4, even then there is a smell of diesel when I drive with the window open. No fuel leaks are visible and my mpg is fab (56 mpg on a recent trip to Spain using Excellium). My mechanic says it may have to do with a fuel return system, but it passes an MOT by not over filling. Thanks for your tips, very much appreciated.