From:Dave Hennessey
Subject:RE: gas cap seal Date:Mon Jan 29 02:08:14 2018
Response to:22470
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 screws.

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 break.

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 success.

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


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

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