I've got minor surface rust on the interior of my fuel tank. Since I'm pulling the tank out for other maintenance, I might as well handle this too.

Any thoughts on the best way to handle this job? I know there is some controversy about the Eastwood/POR kits.

thanks,
Rusty

I used the POR kit with good result. I suspect the people who didn’t get as good a result didn’t follow the instructions to the letter? I did get burned by one of the chemicals when my duct tape improvised tank seals got leaky during the sloshing. The inside of my tank is pristine silver finish. I did mine at least a decade ago.

Thanks for the advice, Rob.

Chemical burns? Yikes. What would you have chosen instead of duct tape?

Long time ago, I remember someone recommending taking a tank to a radiator shop for boiling. I wonder if that would strip the paint off the exterior? I'd rather not have to paint the outside.

I just did this over the past week. Mine had quite a bit of rust. What I did was take mercuric acid and water with a 50/50 ratio. I used a gallon of MA. Then shook the the daylights out of it. Then let it set 10 to 15 mins per side. Poured it out and washed out the take with water. It removed a lot of rust. Then I purchased a fuel tank sealer kit off of Amazon. I reflushed it again with the cleaner to get any additional rust, let dry. Poured in rust prohibitor and shook it around. Poured out and let dry. Then put almost 2 quarts of sealer and let dry for a few days. It is not a quick process. Takes a few days to do it right. Mine turned out great. Like I said, I had a lot of rust. Be sure to treat any outside rust as well if you have bubbling.

I was wishing for big rubber plugs but there just isn’t anything large enough for the top holes. The chemicals in the POR kit are no mystery. I recall muriatic acid which is common pool store fare. If I did it again, I’d find a rubber chem suit. The biggest risk is to your arms as you have to roll the tank around to distribute the chemicals. Maybe an old welding jacket?

I have to do the 240Z tank and I’ll probably just do the radiator shop method. But that’s
because my uppity gated guarded community doesn’t lend itself to working on cars. People have done that forever with good result. Not much price difference.

I had my tank commercially "boiled out" without realizing that process would also remove the external mounts for the vapor tank and charcoal canister. I later discovered I could have bought a replacement tank for less that the boiling cost.

If its truly surface & you want to DIY simply go to favorite store PU a few gals of some apple cider vinegar with a min. 5% acidity fill rotate every couple of days rinse out with water dry & fill with fresh petrol

That's what I did with one 914 tank and a couple motorcycle tanks. It will rust very quickly once the vinegar is cleaned out so if you aren't filling it up with gas, coat with some Marvel Mystery oil or similar.

+1 Did it twice - first time I really took my time and it turned out great. The tank was NASTY, but came out looking great and is still in great shape (~ 5 years ago).

Second time I think I may have rushed things a bit, and I wasn't as happy with how it looked. That tank is still sitting on a shelf, so I don't know if it's going to last or not.

It is awkward holding that tank up and trying to slosh around everything inside of their properly.

When you slosh the tanks around, add some roofing nails or 1 inch deck screws.
Put the tank into an old tire and just roll the tire all over (which will roll the tank as well). This will save your arms while you are sloshing the tank around for an hour.

Zach

Rob - I have some extra tanks if you ever need one. No charge for you buddy. Mark

I show this every so often
Click to view attachment

The filler hole is covered with a disc of plexiglass screwed on with the normal screws sealed with RTV. Tank is filled with phosphoric acid, chain lengths and bolts. Count the pieces as you put them in so you are sure to get them back out. Have done this with three gas tanks. Didn't seal because I don't know how well the sealer works: does undercoating prevent rust?
Makes one hell of a noise. Can substitute gear motor or electric drill to drive the rotisserie. Or use the gear motor from an old bar b q rotor.

@Rusty

I've got minor surface rust on the interior of my fuel tank. Since I'm pulling the tank out for other maintenance, I might as well handle this too.

Any thoughts on the best way to handle this job? I know there is some controversy about the Eastwood/POR kits.

thanks,
Rusty
[/quote]

I have used acid, vinegar,lemon juice and Evaporust.
I dont like acid for several reasons. It seems to remain in the seems and continue to rust.
2 gallons will do it but 5 is better. Make block off plates for the sender and filler holes. Rotate and let sit for several hours on each side. I did 2 Tanks with 5 gallons and used it afterwards to unrust m as my more pounds of parts. On sale at northern tool. I get it at oreilly auto parts for $25 a gallon
Bruce

@Rusty

I've got minor surface rust on the interior of my fuel tank. Since I'm pulling the tank out for other maintenance, I might as well handle this too.

Any thoughts on the best way to handle this job? I know there is some controversy about the Eastwood/POR kits.

thanks,
Rusty
[/quote]

I have used acid, vinegar,lemon juice and Evaporust.
I dont like acid for several reasons. It seems to remain in the seems and continue to rust.
2 gallons will do it but 5 is better. Make block off plates for the sender and filler holes. Rotate and let sit for several hours on each side. I did 2 Tanks with 5 gallons and used it afterwards to unrust m as my more pounds of parts. On sale at northern tool. I get it at oreilly auto parts for $25 a gallon
Bruce

@bdstone914 Did you use a sealer after?

Wow this was a hard thread when you could just clean it. Rocket fuching science.

Thank you, Mark! You are always generous. Need to get my project teener down to my new place and start again before I need another tank.

@Rusty
no sealer. original tanks did not have any. There are some dealers out there but if they do not adhere they can plug up the ports.

the por cleaner works very well we just do not coat the tank with the liner stuff that is for sure!!!

This is genius.

I like the evapo rust. But it works better warm and it doesn’t last forever. Hard to know when it is no longer active.

The external mounts are not welded? Can they removed and mounted on a new reproduction Dansk tank?

Apparently they are soldered in place rather than welded.

Rusty:
The best and most economical way is to go to your local grocery store or Costco and buy 6 gallons of white distilled vinegar. Then go to your Home Depot, Lowe's, or ACE Hardware and buy two plumber's test expanding rubber tipped plugs: one for the big hole for the gas tank filler neck and a smaller one for the gas tank sending unit hole. Alternatively, you can leave the sending unit in the tank with no ill effects. Leave/put back all the small threaded bolts that hold down the filler pipe and the gauge sending unit screwed into the tank to seal up the small mounting holes.

Next just put a length of fuel line hose to connect the two bottom tank outlets; or, as I did, remove both of the the outlet pipes and connect a piece of old heater hose (either 5/8" or 3/4" inside diameter - I can't remember) from one threaded outlet to the other on the bottom of the tank.

Pour all the distilled vinegar into the tank and replace the plumber's test plug. Let the tank sit on its side for a day. Next day turn the tank over so the vinegar can cover the other inside half of the tank.

On the third day, drain out the vinegar and refill the tank with a combination of water and a box or two of Arm and Hammer Baking Soda to neutralize the acid. Let the baking soda and water sit in the tank for a couple of hours, then drain it out and flush the tank with water to rinse it all out.

Then dry out the inside of the tank using a hair dryer pointed into one or both of the big holes.

Once the inside of the tank is dry, pour a quart of Automatic Transmission Fluid into the tank and slosh it all around to prevent "flash rusting". When you are ready to put the tank back into the car, turn the tank upright and drain out the ATF and put the tank back into car and fill it with gas.

You will be amazed at how this cleans out all the rust. I learned this from watching YouTube videos on how to clean motorcycle gas tanks and used it on my 914's tank a year ago. It worked perfectly. No need to worry about disposing of hazardous chemicals or breathing dangerous vapors from the various snake oil products sold by Eastwood, Por15 or others looking to empty your wallet. No need to use expensive gas tank coatings of dubious effectiveness on the inside of the tank.
Mike D.

I used to have a small coffee can with KEPS nuts, chain, fence staples, bolts and sheet rock screws that I used to clean a tank. I don't mind cleaning the tank so much, but the old bad gas; now that's nasty