Shoer Fuel Tank Sealing


Larry Shoer, Massachusetts, USA (larryshoer at comcast dot net)

Earlier this spring I asked some questions and did research on gas tank sealer kits I might use for my 1952 MG TD fuel tank. My objective was to clean the inside of the tank, seal the interior surfaces, and not damage the exterior paint. I’ve now completed this work and am very pleased with the results.

I used POR-15 Marine Clean to clean sludge out of the tank, POR-15 Metal Ready to etch the tank interior, and Caswell Gas Tank Sealer to form an epoxy lining on the interior of the tank.

Detailed directions can be found in the archives. I modified the procedure described by Michael Balahutrak on July 24, 1998. Refer to Mike’s procedure for more details.

After removing the tank from the car I sealed all openings except the fill port. I poured into the tank a coffee can’s worth of different sized small steel balls. I added about a gallon of water, agitated the tank in every which direction, then emptied the water through the fittings on the bottom of the tank. I returned any steel balls that fell out back to the tank, added more water, and repeated this process until the water came out clear and colorless. Again I returned steel balls to the tank. I added about one quart of Marine Clean, hot water as instructed, and agitated the tank on and off for several hours. The solution appeared dark brown when drained. I repeated the Marine Clean rinse procedure. I repeated the Marine Clean rinse a third time and let the solution sit overnight in the fuel tank. The next day I agitated the tank on and off for several hours, then drained the tank. Only some small particles appeared to settle out of the water, which had the color of French onion soup. I rinsed out the tank repeatedly with water, sometimes sloshing a couple gallons around at a time, other times filling the tank completely and draining out the water. The water came out clear and colorless.

I added about one quart of Metal Ready and agitated the tank over several hours. I dumped out the Metal Ready, added a fresh quart of Metal Ready, and agitated the tank again over several hours. I repeated this process a third time. The Metal Ready treatment spanned two or three days. Finally, I rinsed out the tank repeatedly with water, sometimes sloshing a couple gallons around at a time, other times filling the tank completely and draining out the water. The water came out clear and colorless. All the while I did the Metal Ready rinses the steel balls that came out of the tank were set aside and not returned to the tank.

I then dried the tank beside my heating furnace for a week and a half. I used a small 12 volt muffin fan to continuously sweep air through the tank. At the end of the drying time I used a magnet to remove any remaining steel balls. The tank interior walls appeared a mottled gun metal gray. The very rough appearing rust that was originally on the inside of the tank was almost completely gone.

I sealed the tank with the rubber stoppers I had been using on the fill port and bottom fittings, this time using a double layer of Saran Wrap (plastic wrap) between the tank and the stoppers. I also used a double layer of Saran Wrap between the plate and the tank where the sender unit attaches. I took a clean, dry, one gallon plastic milk container and cut off one side, so as to leave the original opening and handle intact. This allowed me to rest the container on one side and have a large opening on the opposite side, through which I could pour in the epoxy and stir it up. I put the cap on the spout. I used two kits of Caswell Gas Tank Sealer. First I added the epoxy into the container. Next I added the hardener. I stirred the mixture for just over two minutes, as the directions described. Without going into further details, I discovered that this was not sufficient mixing time. (The lengthy time and vigorous motion of the tank which followed caused the epoxy finally to be completely mixed.) I suggest mixing the epoxy for 3 or 3 ½ minutes before pouring it into the tank. I pulled the cap off the milk bottle and used the spout to pour the epoxy into the tank. I agitated the tank vigorously and continuously for 20 minutes, after which I drained the remaining epoxy through the fittings on the bottom of the tank. I used some of the epoxy that drained out to coat the fill port on the top of the tank. When draining was reduced to slow drips, I took a cloth and every couple of minutes I cleaned off the threads on the fittings. I also ran the drain plug in and out of the fitting and cleaned it off, too.

After the epoxy was well along in curing, I put the tank back beside the furnace. A few days later I examined the tank as best I could through the different openings. I could see the shiny, glassy appearance of the epoxy coating on all surfaces. The coating appeared to be significantly more than just the thin coat you would get from a paint-like product. It seemed to be very strongly bonded to the tank surfaces.

I was really pleased with the performance of the materials I used for this project. The Caswell Gas Tank Sealer, in particular, did a very impressive job lining the interior of the tank.

POR-15 Marine Clean

POR-15 Metal Ready

Caswell Gas Tank Sealer From the manufacturer: Withstands modern ethanol fuels


Posted 01 May 2008 at 16:36:19 UK time

Francis Precht, Maryland, USA,

What strategy/technique did you use to provide all the agitation for, as you describe, several hours ?? Sounds like quite a work-out!

Posted 02 May 2008 at 02:26:21 UK time

Larry Shoer, Massachusetts, USA (larryshoer at comcast dot net)

When the epoxy was in the tank I agitated, shook, rolled, flipped, etc. the tank continuously for 20 minutes. That was the longest continuous agitating of the tank I did.

When the tank was loaded with Marine Clean or Metal Ready I agitated the tank for about five minutes, then set it down in a different position from where it was positioned last. This might be the left or right side, upside down or rightside up, back or front. I'd let the tank sit that way anywere from 30 minutes to overnight, then continue the process. I just interrupted whatever chores I was doing during the day or evening to spend five minutes with the tank.

The water washes involved more continuous effort. I added water to the tank, agitated, drained, refilled, etc. My "stand" to hold the tank when I filled it to the top with water consisted of two inverted plastic trash barrels. The tank bottom rested on the barrels and the back leaned against a wall. This was also my "drain stand" for the other washes.

Although this is a project that takes many days, it mostly takes short bursts of time along the way.

I did consider building a more elaborate stand to help when agitating the tank. Since I'm 6'2" and lanky I was able to move the tank around without too much difficulty.


Posted 03 May 2008 at 02:10:07 UK time

Larry Shoer, Massachusetts, USA (larryshoer at comcast dot net)

I exchanged e-mail messages with Mike Caswell, owner of the company that sells the gas tank sealer I used. Mike suggests that the epoxy and hardener be mixed in one container, then poured into a second container, and the mixing be completed in the second container. This promotes good mixing of the materials.

If I was doing this again, I would mix the epoxy and hardener in one container for about 1 1/2 minutes, pour the mixture into a second container, and continue the mixing for an additional 1 1/2 minutes. I used an old kitchen rubber spatula to mix the epoxy and hardener.

The instructions say to leave the epoxy in the tank "for several minutes to obtain a good layer of Gas Tank Sealer over all surfaces." I called Caswell before I did this work to find out what they recommended as the maximum amount of time I could slosh the epoxy in the tank before draining it out. Given the several baffles in the tank I wanted to make sure I had plenty of time to work the epoxy into all corners of the tank. I was told that leaving the epoxy in the tank for approximately 20 minutes would be fine. The epoxy flowed out smoothly after 20 minutes and I am sure I could have left it a few minutes longer without problem.

The epoxy, hardener, and tank were at 70 degrees F during this process. Make sure the temperature is close to this if you follow my procedure. Epoxy will cure more quickly if you start with elevated temperatures.



(508) 746-6735