From:backyard bob e-mail:somewhere-A-newjersey
Subject:RE: RE: gas cap seal Date:Tue Jan 30 11:15:15 2018
Response to:22472
I heard somewhere that gas tanks can be boiled out at
radiator shops (are there any left?). I've also heard
that IPA (isopropyl alcohol) displaces and evaporates
water. I also used 'gas tank creme' a long time ago and
had to throw the tank away after gasoline turned it to
tar sludge after a week. I've used POR 15 industrially
and it works fine. If rust is the only problem try mixing
molasses with water and filling the tank for 2 weeks
(Google it. I tried it on a cylinder and it worked

Over the years I've heard the highest praises, and some
horror stories, about every brand of tank sealer.

I think the reason for the horror stories is that people
did NOT follow the directions.

When the directions say use cleaner solution A until the
tank is clean - it means CLEAN. Not kinda clean. Not
pretty clean. Not almost clean. It means CLEAN. Same
goes for cleaner solution B.

When it says dry the tank, it means DRY. Not pretty dry.
Not almost dry. It means DRY.

The actual sealer is some kind of super-duper-paint.
Paint does not stick to gunk and glop. Paint does not
stick to water. If the inside of the tank is not 100%
CLEAN and 100% DRY, the sealer will not stick.

I did a K-model tank, which is much more "open" inside
than a Hummer tank, which has a very tall "tunnel". My
tank was very rusty inside, and had a lot of dried glop
from where a tank of gasoline had slowly evaporated over
20 years.

First, I put a large handful of sheetmetal screws (or
deck screws) in it. These have a lot of sharp edges on
them - nuts and bolts do not. Shake, shake, shake. Turn
tank 45 degrees and shake. Turn and shake. Take a break
until you regain feeling in your arms. Drain the screws
and rust, then put the screws back in. Continue shaking
until almost no rust comes out. I probably shook for
four hours over several days. It takes a long time!

Some people say wrap the tank in towels, tie or tape the
towels on, then put it in the clothes dryer with a bunch
more towels. I didn't do this, but it gives you an idea
of how much shaking is involved.

On the Hummer-series tanks you can see half the inside
through the gas filler hole, but you can't see on the
other side of the tunnel. The other side may accumulate
more glop and rust than the visible side. For the
shaking and cleaning solutions steps, make sure you pay
more attention to the unseen side - it probably needs it.

When I did cleaner A (the one that breaks down dried gas
glop), it didn't come clean in the amount of time the
directions said. I had to let it soak for double the
amount of time - until it was CLEAN. I think the cleaner
B (rust remover) easily came clean in the directions
amount of time - due to all that shaking with deck

Drying is much more difficult that you would imagine. I
used compressed air though the filler hole and petcock
hole. Turned the tank left, right, upside down. Then I
used a heat gun (like you'd use to scrape exterior house
paint) stuck in the filler hole. Let run for 30 minutes,
turning left, right, upside-down. Then look carefully
inside the tank - at the corners. You may see a teensy
bit of water in a corner. The sealer will not stick to
water - so the tank must be completely DRY. One little
spot where the sealer doesn't stick will give gasoline an
entry point to get under the sealer.

With the Hummer tank's high tunnel, it may take a couple
of hours of heat gun. Burn some kilowatts! Heat, turn,
blast with compressed air. Repeat. Do it again tomorrow.

The sealer itself is like thick paint. You have to let
it run and turn the tank, and let it run and turn the
tank to coat all the surfaces. Once you start, you have
to continue until the tank is completely coated. It
starts to dry fairly quickly, so don't stop to take a

Tank and chemicals should be at room temperature. The
cleaners will work better at room temp. The sealer will
flow better at room temperature. My garage here in
Virginia is too cold this time of year.

Plug the petcock bung. The sealer is tough to get out of
the threads. I think I used a rubber stopper that I
ground down to be more cylindrical.

I hope I haven't scared you off this project. I just
wanted to emphasize CLEAN and DRY as the secrets to

I'd like to hear about others' experiences with tank


I'm getting ready to clean out my gas tank with POR-15.

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