ISSUE 419 • GARAGE BUILD • 575
I use a radiator test kit’s hand pump to pressurize
a tank. Since the kit’s caps didn’t fit the gas cap
opening, I removed the hose’s fitting so I could
connect it directly to the tank’s vent tube.2
If working on a painted tank, completely cover all
painted areas with multiple layers of blue paint tape
and then duct tape. This should help protect the
paint from drops of cleaner and sealant.
1
Before I send a gas tank out to be painted, I want to
make sure it doesn’t leak. If there’s any internal rust, I
clean out the rust and then coat the inside with sealer.
3
Put a layer or two of duct tape over the gas cap threads
in the filler neck to prevent fluids from getting under
the edge of the outer layers of tape.
4
Here’s what a painted tank should look like when
properly covered with blue painting tape. I completely
cover the blue tape with duct tape.6
After filling a sink with water, completely
submerge the tank while a buddy keeps about
3 psi of air pressure in the tank as you both look
for air bubbles.the vent hole with duct tape. Or you
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closed. If you do use tape to seal a hole,
you’ll have to cover the tape with your
hand to keep it sealed tight once the
tank is pressurized.
To seal the petcock/fuel port bung,
you can use an old petcock or the
proper size pipe plug (the better option)
with the threads wrapped with some
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a vent tube, pressurize the tank via the
petcock/fuel port using an old petcock.
Or, as we did with a custom tank (the
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proper pipe thread size on one end.
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saddle tank, which has a vent tube on
top and a fuel crossover tube on the
bottom. Using one of these tubes is the
safest and easiest way to add air to the
tank. We used the fuel crossover tube
as our air source, and the other tube
was sealed with a rubber hose, two hose
clamps, and the proper diameter bolt
with a shank that has a smooth section
(no threads) at least 3/4" long.
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or bucket that’s deep enough to com-
pletely cover the tank with water with
5" to spare. Then have a buddy add 3
psi of air pressure as you hold the tank
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cover any sealing tape with your hand.
If you see air bubbles around the gas
cap, it’s not a problem as long as the
bubbles are coming from the cap and
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The same goes for your petcock/fuel
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where the petcock’s threaded bung
joins the tank, you’re good. Bubbles
coming from where the petcock/fuel
port threads into its bung is not a
problem. If you see bubbles coming
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the hole to stop the leak. Then, while
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mark the spot, pull the tank from the
water and mark where the hole is
with a black marker. If you don’t see
air bubbles coming from places they
shouldn’t, your tank is good to go.Clean & Seal
Once you know your tank is tight, it’s
time to clean out any rust and then