Fuel filler cap

[robmc52]

The filler cap on my w210 seems to let fuel past on a regular basis. Although I couldn't see anything obviously wrong with it I bought a new cap. Naturally the new one hasn't made any difference, it still leaks. Does this mean there's a breather or something blocked somewhere? What with all the mud over it and streaks of diesel down the bodywork it looks like a dogs dinner at the moment

 

[turbopete]

probably from overfilling or dribbles from the nozzle after filling

 

[robmc52]

I did think that at first but it seems to happen regardless of how full the tank is and I always give the area around the filler a wipe after filling up.