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I replaced the gasket that seals the fuel pump access cover in the top of the fuel tank. I noticed gas fumes inside the car and after filling the tank one day I parked it nose down hill in my parking lot. Gas was running out in front of the left rear wheel well. Moved the car around and removed the inspection cover under the rear seat (fuel pump access ) and saw that fuel was leaking around the gasket. Replaced it with a new Mazda unit, but it still leaks! The mating surfaces are fine, no rust or defects. Just wondering if anyone else ever had this issue. I did notice that the original gasket had what appeared to be some type of a "film" like maybe a thin coat of a factory sealer on it. I have some fuel resistant permatex, but I know there aren't many affordable fuel resistant sealants available. Porsche used to have a very expensive sealer that they used for these type of issues ( we used some once to repair a minor fuel cell issue to get us through the race season until we could send it back to the manufacture for a real repair) but is there anything else out there? I have MotoSeal 1 Ultimate Gasket maker Grey that I may try, just wonder if anyone else ever had this issue? Gasket cost $22.00 from Mazda, so I don't want to try my luck with another one...yet! Tank is full now, so I need to burn off some fuel before I try the sealer...once I get the clutch slave bled properly. Nothing like a 21 year old car and no garage!
 

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did your seal come with new screws? I had this issue a few months ago when I got the car going. First it was actually the return hose that had a hole in it, then I found it would leak from the seal so I ordered one from RockAuto that came with new screws and that solved it. Might be worth it to try sealer though.

edit: btw if I remember correctly, the gasket from rock auto was $11 shipped.
 

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Did your seal come with new screws? I had this issue a few months ago when I got the car going. First it was actually the return hose that had a hole in it.

I had this same problem a couple of years ago. The return line had a hole in a place where I had to actually drop the tank to repair it. I took the opportunity
change fuel pumps so the access cover came off. The difference was that while my seal was good, my tightening of the screws was bad so I had a leak when I had a half a tank or more. The obvious fix for me was to tighten the screws down better. I will admit though that those tiny screws suck when they get older. The heads are soft and are not meant for repeated use so new screws are not a bad idea.
 

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if you can replace the screws with hex head or cap head ones ( I think theyre 4mm ISO thread from memory)

I damaged the heads on nearly all of mine undoing them, and then couldn't tighten them up enough to make a good seal.
 

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Discussion Starter #5
Thanks. Hadn't thought about changing to a socket head or cap screw. I did go back and replace the original ones, but with used ones I removed from a junk yard car.
 

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Hrmm... wonder if this is the problem on my car. I just stopped filling it more than 2/3rds full, and haven't had an issue yet.
 

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there is a silicone avail that is resistant to gasoline. i had to use that on my tank, i believe the top of the fuel tank warps a bit after so many years and makes a tight seal impossible. youll know it when you start smelling fumes or literally leaking gas out of the top
 

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Hrmm... wonder if this is the problem on my car. I just stopped filling it more than 2/3rds full, and haven't had an issue yet.
So, you don't go around corners fast? Mine still smells even if it's over half full because it sloshes around and still leaks (and smells):mad:
 

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Discussion Starter #9
there is a silicone avail that is resistant to gasoline. i had to use that on my tank, i believe the top of the fuel tank warps a bit after so many years and makes a tight seal impossible. youll know it when you start smelling fumes or literally leaking gas out of the top
Yes, I have some of that Permatex, but haven't tried it yet. I'm going to try the socket head screws when I do the silicone. I just finished a slave cylinder and clutch master cylinder replace and my tank is still way too full. I need to burn off some fuel before hand..
 

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So, you don't go around corners fast? Mine still smells even if it's over half full because it sloshes around and still leaks (and smells):mad:
I live in Indiana. I don't know what corners are. :p

And if i did, i don't think my shitty Nexens would hold on long enough for the fuel tank to realize that there were lateral Gs involved.
 

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I have this same issue, but I think mine is leaking on the front side of where the two peices are sealed together. If I fill it over 3/4 of a tank it will leak out slowly. I want to swap it out for a new fuel tank due to the fact that the fuel pump door screws are a stripped out
 

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Discussion Starter #12
Well, replaced gasket and swapped the screws to socket heads..still stinks! I guess, for now it will. Have some road trips to do, and other issues come first. Just thought I would update everyone.
Thanks!
 

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Thats frustrating.

Maybe its residual fuel vapours....It might clear up after time.

If not maybe its worth pressure testing it. I am not sure what the rating of the system is, I'd guess maybe 5psi or something like that. It has to be able to take the vapour pressure on a hot day.

You could pressurise the tank to 5 psi by putting a regulator and feeding air into one of the return lines and then use the soapy spray test around the flange to see if youre getting bubbles.
 

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Discussion Starter #14
Still have this issue. replaced the gasket again, doesn't help. I'm not driving the car much these days as I'm laid off and not commuting these days. Blue car with no AC in the south is just unbearable in the summer.
 

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There are 2 vacuum fittings on the rear upper drivers side of the tank, the metal nipples often rust away where they are connected to the tank. Perhaps they are leaking and causing the gas smell.
If you do have leaks, jb-weld quick hold up to fuel. to fix a leak clean the area, mix 1/2 the jb weld and cover the area (and hole) with a 3 to 4" diameter coating, let it dry, scuff it and apply the remaining jb-weld over a 5" to 6" diameter area . This works well for gas tanks and oil pans.
I once changed my drivers axle seal 7 or 8 times because it was leaking, until I realized it wasn't the axle seal, the powder coat on the transmission housing wore down under the bolt heads and the transmission housing was leaking at the seam, but when driving (at high speeds all the time) the gear oil covered the driver axle seal and axle end making it look like the axle seal was leaking instead of the housing below it.
 
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