Stu-82

I had a similar thing happen when i brimmed my tank at the petrol station one time. I stopped filling and just as I removed the nozzle petrol started overflowing as if there was still more going in, i quickly put the cap on to stop it pouring out then curiously i removed the cap to see what happened and as i pulled it off the petrol rised up and started coming out again so i put it back on and took a longer drive home to bring the tank level down. i haven't over filled it since and not had the problem again. One thing i have noticed when i remove the filler cap when the tank is low i get a hissing air sound, not sure if the pressure is going in or out of the tank but should this be happening unless the breather pipe is blocked??