I was trying to hunt down a leak in my 2010 sport and I tried all the typical things like sealing around the hinges and sealing the areas where the two panels meet on the roof. I tried everything and eventually got to taking off the tail lights, thinking it may be the foam seals around them. When I took the passenger side off, I noticed a tiny little pin hole on the body, right where the headlight mounts. It was found by a helper spraying a hose and me sitting inside the car with the interior stripped out trying to figure out where the leak is, best method I will post photos later but as far as i can tell it seems like the pinhole was there from the factory. This car has a clean title, never been in an accident and none of the body panels and paint point to it never being repaired at any point. Strange thing, figure I would post about it incase anyone else has the headache of trying to patch a leak and your patching or looking in the wrong area. New to forum but will be posting all my mods and interesting things i find for other users. Great forum, used it for lots of info and maintenance.

 

The foam taillight seals can go bad after just a few years. Typical Honda problem that goes back to the 1980's. They dry out and stay compressed. Letting in moisture around them.

Our 2018 Fit headlights and taillights have been leaking moisture since almost new.