56 • GARAGE BUILD • ISSUE 419
Test & Seal
A Tank
TOOLS NEEDED
Blue paint tape
Duct tape
Teflon tape
Black marker
Rubber hose
Hose clamps
Long shank bolt
Pipe plug
Mop bucket
Old non-vented cap
Old petcock/hose fitting
Hair dryer
Hand pump/air tankINSTALL^ • by Chris Maidakeep or it’s naked steel. To do a proper
leak check, you must pressurize the
tank with air and either fully submerge
it in water or use soapy water at pos-
sible leak spots. When a tank is sub-
merged in water, a leak will produce a
stream of air bubbles coming from the
hole to show you exactly where it is. It’s
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tube (remember those?) under water to
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brush the soapy solution onto a seam,
weld, or suspected area, bubbles will
immediately form if there’s an air leak.
The best way to pressurize a small
tank is with a hand pump, like one
for bicycle tires, and an old tire valve.
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tank at the required pressure without
running the risk of applying too much
pressure and popping a seam or caus-
ing the tank’s walls to bulge. I used the
hand pump from a radiator test kit I
own. Since the kit’s radiator cap adapt-
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the pump’s hose so I could connect the
pump’s hose directly to the gas tank’s
vent tube. Resist the urge to use a shop
air compressor and regulator setup
since you’re only going to pressurize
the tank to about 3 psi. These regula-
tors are normally set at 100 psi or more
and don’t regulate very low pressure
settings well. However, you can (if
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sor tank to 3 psi and then attach the air
tank, without the compressor running,
to your gas tank. Whichever method
you use, keep in mind that you’ll need
to replenish any air that leaks past the
gas cap, etc. to keep the pressure at
3 psi during the test.
The next step is to seal all the tank’s
openings, except for the one you plan
on using as the air source. Use an old
unvented gas cap to seal the tank’s
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where the cap’s seal will contact the
tank to reduce air leakage. If your
cap is vented, you may be able to sealW
HETHER IT’S A USED STOCK TANK OR A BRAND-
new CUSTOM one, before sending it out for
paint you should pressure-check the tank
for leaks. Even a small seepage of gasoline
will destroy a tank’s paintwork. If there’s any rust inside the
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and a sealant that’s impervious to ethanol-based
fuels applied. There are various sealing kits avail-
able, like POR-15 or the kit we used from Bill
Hirsch, that has all the solutions needed to clean,
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work now will eliminate future headaches like
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a new tank that didn’t come internally treated
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to prevent future rust issues. Personally, I also
pressure-test a new tank, just to make sure I
won’t have a problem after it’s painted.The Leak Test
When doing a leak test, it doesn’t matter if your
tank is covered with a paint job you want toBefore painting, test a tank for leaks,
clean the interior, and seal it