Wife called me and said it was nearly impossible to remove the gas cap off of our 1994 530.

She said it twisted fine, but that she had a difficult time actually pulling it off, and when it did come off, it made a whoosh (suction?) sound.

I thought it was wierd that she could *twist* the cap just fine, but not remove it.

Is it possible that there was enough vacuum in the system to make removing the gas cap difficult? WHat would cause this vacuum? We've never experienced this before.

Thanks for any and all input.