Gas cap leaks even after new gaskets

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tom coughlin
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Gas cap leaks even after new gaskets

#1 Post by tom coughlin » Fri Nov 02, 2018 9:00 am

It seems that gas is always getting out under the cap (especially with a full tank naturally). I've replaced the cap gasket several times but the issue always rears its ugly head.
I can't believe they did this when new, so is there a better gasket? Do I have a warped cap or filler neck? Have others experienced this? Thanks, Tom
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Rick Albro
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Re: Gas cap leaks even after new gaskets

#2 Post by Rick Albro » Fri Nov 02, 2018 10:19 am

Tom, have you check to see if the vent tube is clogged perhaps with a sealer? Excess pressure will make the cap leak if if the cap normally would not. Have you re positioned your fuel valve? Do you have other inline fuel filters or other modifications? Make sure to check all of the simple things first.

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Jeffrey Leeds
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Re: Gas cap leaks even after new gaskets

#3 Post by Jeffrey Leeds » Fri Nov 02, 2018 10:22 am

Tom, when I'm faced with this situation I put a thin line of Hylomar Blue the on the side of the gasket facing the cap and let it set for a few minutes, and then reinstall the cap. Hylomar is a fuel resistant sealer and doesn't harden so it can be removed/wiped-off at any time. I also use the Hylomar on the valve-cover side of the gaskets to help them in position when reinstalling the cover.

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Vic Skirmants
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Re: Gas cap leaks even after new gaskets

#4 Post by Vic Skirmants » Sat Nov 03, 2018 7:34 am

Tom; is your car a pre-A? Leaking large gas caps have been discussed before. If it is a T-6, then ask this question in the Main Discussion. Good luck.

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tom coughlin
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Re: Gas cap leaks even after new gaskets

#5 Post by tom coughlin » Fri Jan 11, 2019 9:47 am

OK, based on the good advice received here I'm about to repair my '55 pre-A gas cap. My plan is to use Permatex 85420 sealer to fill the multiple openings in the center of the inside cap. I have also read that J B Weld (altered to made it more liquid) has been used but have decided to go with 85420 which already flows.
My goal is a useful fix that is long lasting and uncomplicated to achieve (so it isn't above my pay grade).

Update:
I wrote to Prermatex and was advised not to use 85420. They suggested "E-sealer" from Gasolia which I will use. Tom
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