Can anyone tell me how to get this old rubber out of this gas cap? a It's old and dry and useless and gas leaks out of the tank. It doesn't look to me like the rubber goes around the center metal section but rather most of it seems under the metal. So I assume I have to turn this metal piece counter clockwise to get it off the rubber then lifts right out? Also where would I find a piece of rubber like this as a replacement? Thanks.