I filled up the car on Christmas day. I have driven the car until there was about 1/4 tank left. Now when I go to fill up, I only get about 2.5 litres in and the gas starts to overflow. It will go down, but very, very slowly. After driving, I can hear a suction like sound, and a faint "thunk", when I remove the gas cap... Any ideas? Air lock in the tank?...

The gas gauge is working properly, because I keep track of the mile and it lines up with where it is at...that is the first thing that I checked.

Any suggestions would be greatly appreciated!

Dale