The flap will not close when the gasket is incorrectly installed. Dry fit 1st to check. I think when I last took mine apart, it was not necessary to glue it on. It is amazing all the crud you will find that makes its way in there. There is a guy on Ebay out of Madison, Wisc. that sells some used 113 parts. You can reach him at eurocars@itis.com
Frank Koronkiewicz
Willowbrook, Illinois
1970 280SL Light Ivory