Last weekend I noticed a reddish-brown blob on the garage floor
approximately where the back of the snake normally resides so I started
poking around underneath for the source. Sure enough the fuel line
leading form the gas tank and the bottom of the tank itself were covered
with a film of gasoline. A quick inspection verified what I suspected:
gas was leaking passed the 3/4" pipe threads of the exit fitting. I had
debated replacing this fitting when I had the tank out but decided
against it because I couldn't find anything to replace it with that I
thought would fit properly or be any better. The fitting itself has non
tapered British pipe threads which screw into a 3/16" thick plate
soldered to the bottom of the tank. The problem seems to be that the
contact area of the threads isn't large enough to seal properly so good
sealing depends on using a crushable washer. The old washer was made of
some sort of plastic fiber material similar in appearance to the
material used in some household plumbing washers. I wasn't able to find
another one of the correct size so I decided to clean up the old one and
re-use it. Also I coated the threads of the fitting and the washer with
a thread compound recommended by a clerk at a local auto parts store.
The thread compound seemed like the same goopy grey-white paste I'd
bought in the past from plumbing supply stores. Probably this stuff
would have worked fine for tapered threads with good contact area but it
just wasn't adequate here.
My first shot at a fix was to apply a little more torque to the fitting.
The only wrench I had that fit was a Whitworth from a cheapie set I had
gotten from Moss a while back. Because this wrench is so short I could
only get a small fraction of turn more. There wasn't enough room to to
get an adjustable wrench on the fitting and I didn't want to risk
rounding off the soft brass flats with the wrong size wrench. Needless
to say, this didn't work.
So now my assignment (which I've chosen to accept) is to drive the car
until the tank is nearly empty, drain it, remove the fitting and come up
with a fix. I wish now that I had kept a little of the slushing sealer
I had used inside the tank. Bet a bit of that on the threads would have
sealed things nicely. I've been thinking about using petroleum
resistant Locktite as a thread sealer. I've had a couple of
unsatisfactory experiences with silicone sealers so I'm ruling them out.
I did find what I think is a nylon washer of about the right size at
Orchard Supply Hardware, but I'm not sure how nylon gets along with
gasoline. Another idea I've been kicking around is to make a gasket out
of some neoprene rubber sheet I had left over from the tank
installation. I used this in place of the original paper-like strips
that were on the frame members the gas tank rests on.
BTW, the reddish-brown puddle that started this all off turned out to be
oil and had nothing to do with the tank leak. A mystery yet to be