I also have this problem... at first I thought the leaking was the tank itself, but I got my cousin to take a look at it (Mazda employee that did mechanic and now he's the parts manager) and he told me about this well known issue of the gas pump housing leaking from the top... so he removed the back seat, removed the first metal cover and then discovered that the top metal ring screws were badddddllyyyyy damaged by corrosion. He tried 1 or 2 tools to remove the screws, but they are so badly corroded that they fall apart like dirt... when all the rusted metal is gone, there's only a little bit of good metal left, look slike not enough to do anything to unscrew them. My cousin told me that all the case they resolved at Mazda weren't THAT corroded, he never saw that much rust there.
The only thing I would try would be to make a slit in the head of the screw (if enough metal, I can't remember now) and remove it with a flat screwdriver.
We also checked if the gas tank would be removable, in order to change the whole tank/pump assembly but when he tried to remove the big bolts (6 or 7) under the car, they too were too much rusted, he tried hard to remove one nut, but he felt like they would snap. 3 or 4 of them never moved a mm, 2 or 3 of them moved but were very hard to unscrew. Plus, many lines were in the way of the tank and those lines looks bad and would snap under any bad/medium pressure, so they would have to be disconnected, maybe breaking when disconnecting... so removing the tank for another one from the scrapyard isn't really an option.
I would try again to remove those screws, but in the case it fails because not enough metal is sticking out, does anyone of you think I can drill through them? I would of course take/pump the gas out of the tank first and clean the top with water and maybe even have water flowing on the top while drilling...
Or I even thought maybe popping/sawing the heads off so the cover can be removable and then working on removing the screws stud out of there...
I am very discouraged with this issue. The car is getting old and has a lot of mileage on it (215,000ish km, most of it on highways), but the engine is running very well, had the coils replaced, new brakes... I would like to keep the car but it is wasting way too much gas now... I barely make 300km on a tank while I was doing 500+ per tank... plus the smell is awful.
I put some "dumdum" (black tacky thing) around the edge of the first black metal cover so the fumes would mostly stay outside and up until now, it worked pretty well.
But now this has to be fixed, or I might need to replace the car and put this one down to the scrapyard... which is a shame because the engine is running very well.
I could post some pictures of the state of the rusted metal cover when I'll be able, so it helps you visually.
Thanks for any help anyone can provide, I think my case might be the worst in this thread... it probably looks even worst than "Astral" in page 4... sadly... :'''(
At least, I can see the white of the top of the housing, it's not that dirty, but very corroded.