Gas tank return air valve?

[works]

My gas tank's return air valve seems to be malfunctioning. I haven't run into problems of feeding the engine yet, but after a drive I can hear the gas tank creaking from contraction since the air pressure in the tank has severely dropped; gas goes out but air to replace the lost volume doesn't come in. The only way to relieve it is to open the gas cap and hear the air being sucked in and the gas tank returning to normal state.

Has anyone had similar problems or know where the gas tank's return air valve is located so I can take a look?

 

[Cowui]

Iam having same issue on my vw rabbit 07 did u figured out ?