Back end leak!

[Hardnut]

It sounds like overfilling to me.A garage that I use frequently has a slight slope on the forecourt & going in 1 way I can get it really full.If I then don't go far it will weep slightly.Fill to 1st click & no prob but I tend to round up to next full litre.alut:

That !maybe! onto a winner, did fill it up at station never used before and it on a slight encline. As normaly go for a 2nd click.
Not notice the issue before.
Got an idea how to test it as well. Cheers