Tank Cleaning and Coating

September 25, 2005 to October 22, 2005

The general plan was to remove the tank, clean it, coat the inside with POR-15 Fuel Tank Sealer, paint the outside, then re-install the tank.

First step is draining the tank. There were about eight gallons in the tank when I started. I found rust in the drained fuel so I filtered the gas though an old sock. The filtered gas was then burned in my other cars.
Next step is pulling the tank. The picture at left shows the bracket that supports the gas tanks filler neck. The filler neck is at the upper left. The bracket bolts to the frame rail with the two bolts at left. The band that secures the filler neck was rusted almost to nothing and broke when I removed it. I was going to fabricate a replacement but realized a hose clamp around the remaining portion of the bracket would be a lot easier and probably work better. So that is what I did.
Once the filler neck was loose I disconnected the fuel gauge sensors wiring harness, disconnected the fuel line from the tank, removed three bolts holding the tank to the frame cross-members, then wiggled the tank out of the car.

60+ years worth of road grime was wedged between the top of the tank and the floor of the trunk. This became the first installment of dirt dumped in my face on this job.

When I removed the tank I could hear junk rattling around inside. After removing the fuel gauge sensor I dumped in some ball bearings to help loosen the rust then shook the tank for a while. This is what I got out the first time. I eventually filled up a quart container with tank debris. The crud appears to be about 2/3 old fuel varnish and 1/3 actual rust.
The car (and fuel tank) were heavily undercoated. When I started cleaning the outside of the tank I found that the undercoating had held up over most of the tank but the coating had hardened and was flaking off in many areas. Under the coating was bare shiny metal. The only rusty areas were on top of the tank where the undercoating was never applied. The picture at right shows a close-up of the undercoating and some of the clean metal.
There seemed to be no help for it. The undercoating needed to come off. Scraping with a sharp scraper seemed to be the best method. So I scraped, and scraped, and scraped. Then for variety I scraped some more. This picture shows the bottom of the tank as I really got rolling on it. I spent two days getting the tank cleaned off. In the process I found old damage to the tank that had been repaired with melted lead. Fun!

After all the scraping here was the payoff. I used kerosene and fine steel wool to remove the remnants of the old undercoating and was rewarded by a tank that looked amazingly good. You can see the in the picture at right that I have the left side cleaned. The right side has not been cleaned yet.

Here you can see the results of the external cleaning. The rusty area on the upper left is where the undercoating never got.

Once the outside of the tank was clean it was time for the inside. The cleaning kit came with two quarts of cleaner to remove gunk from the inside of the tank. As recommended I mixed each quart with hot water and shook it in the tank for 20 minutes. Lather, rinse, repeat.

Here is what came out of the tank after the first “wet” cleaning. As before I used ball bearings to help knock loose the crap. After the cleaner a phosphoric acid mix went into the tank to help remove the rust. Finally the tank sealer went in. To keep the sealer from clogging the fuel pickup tube I rigged up my compressor to keep air flowing through the pickup at low pressure while the sealer cured. I was pretty busy doing all this so I did not get any pictures.
After the sealer cured I finished the outside of the tank. I brushed on rusty metal primer first. The primer is wet here which is why it looks glossy.
The top of the filler neck sticks out of the fender of the car. There was a little rust pitting around where the fender’s gasket rubbed the neck. I decided to make the end of the neck look as nice as I could. After sanding the rust off I applied multiple coats of primer and body putty.
The rest of the tank I painted with flat black enamel.
Once I had filled in all the imperfections I painted the neck satin black.
Once the paint had a couple of days to cure I used spray undercoating to undercoat the entire tank.
And finally the tank is back in the car.

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