I think I might have a little problem with my fiesta. When ever I open up my fuel filler cap it is under vacuum?? Just wondering if its the breather that is getting block and if so where is the breather on the car and what is going to be the best way to fix this.

Thanks Guys

is it running empty when you are filling up and you hear this noise?

No I get it all of the time when I open up the fuel cap whether its nearly empty of when its nearly full. Its on a 1.25 petrol as well.

My mk6 used to make that sorta hissing noise everytime i opened it i think its normal mate :)

Mines the same, I presume it's pretty normal too. Although the majority of the time I fill up is when the cars near empty (oopsies!) I just think of it as my car giving out a big sigh of relief that it's finally getting filled up! :D

yeh my car does the same from time to time i would not worry

Ok thats brilliant thank you very much guys. Just wasn't sure if it was a problem or not that would need fixing but thank you for the reassurance!