Hey, got lots of good advise on fixing the gas tank leak in my Cobra but
I think there may have been some mis-communication on my part so let me
expand a little on the problem.
The fitting that screws into the bottom of the tank is brass and has 14
non tapered pipe threads/inch which apparently is a BSP size. At least
none of the hardware stores in my area stock fittings of this size. The
threaded part of the fitting is about an inch long. So far so good.
The bad part is that it screws into a 3/16" thick brass plate which is
soldered to the bottom of the tank. That mean that the contact areas is
only about 2 1/2 threads wide. On top of that the tolerance for this
connection is very sloppy because about ten years ago some, er, idiot
got this plate too hot with a propane torch and warped it. This meant
that the threads had to be lapped with valve grinding compound to get
things to screw together without having to use a breaker bar. Another
problem is that this same idiot bunged up the faces of both the plate
and the fitting so that the original rather stiff but crushable washer
no longer has enough flexibility to make a good seal.
Probably what I should have done was to replace the plate and fitting
when I had the tank out recently. Not doing that seemed like an okay
idea at the time but in retrospect... Well, anyway replacing them now
really isn't an option. I would have to remove the tank again. I ain't
gonna do that. Then I'd have to unsolder the old plate and solder in a
new one. But that would destroy the slushing sealer inside the tank
around the plate; maybe beyond. I ain't gonna do that.
One option that is open is to get a more crushable washer. Chris K.
suggested a Dowty seal. That sounds like a good idea to me and they are
available from Dave Bean. Teflon was also suggested but I'm not sure
where I would get something the right size. I don't think a copper
washer (like the kind used to seal banjo fittings) would be flexible
enough to do the trick. If I had some way to get good flat surfaces
again, maybe. Another option is to seal the threads with some kind of
fuel proof goop. Various Permatex sealers have been suggested and I
even received and offer of some tank sealer. But this would be strictly
a back-up measure since the thread contact area is so small. The
question is: should I use something that hardens (like the tank sealer
and some Permatex goops) or something that stays soft (various other
Permatex goops). This is a small area to seal and snakes do jar around
a bit on the road.
Roland "pit of snakes" Dudley
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