Rusty gas tank help

[Dave Sherman]

This is for the 1947 Lincoln. After much Googling, and despite success with the Honda motorcycle's rusty gas tank, I'm not having much success with the Lincoln's tank. When I got it, it had a few gallons of stale gas, some water, and lots of rust. In fact, the tank sender's brass float and the float arm had rotted away. I have a new sender, thankfully. The tank itself is driving me nuts!

I put a few gallons of vinegar in it initially, and it cleaned up the bottom nicely. I can see about 1/2 of the tank through the filler neck and the sender opening, there's a baffle making it difficult to see anything on one side. The vinegar cleaned up the bottom alright, but there was a line of rust along the sides. I tried some Rust911, and after a couple of days, it turned black as coffee and I couldn't see the bottom of the tank. After draining it, the bottom and the baffle were looking much better. I sloshed it with some WD-40, but after a week, it was rusting again. Perhaps I didn't get all the water out. I put a couple gallons of gasoline in it, and a box of wood screws, and after shaking it up, I could hear LOTS of crud coming loose. I went through a few rounds of that, straining the gas through a paper towel and getting lots of clumps of rust out. I switched over to water from the garden hose, leaving the the screws in there, and after about 15 rounds of fill, shake, and dump, it's still getting lots of rust out of it. I've got some more Rust911 on order, but one big question is, how can I keep it from rusting until I can get it back in the car and get some gas in it? As for the bulk of the rust, should I just keep up with the water and screws and just keep doing the fill, shake, and dump until it's clean coming out?

 

[Nick1994]

I've seen videos before of people getting some ratchet straps and either strapping it to the tire on your pickup, jack up the pickup, then let it idle for a while with some nuts and screws inside to break it all loose. Or if you've got a little cement mixer to strap it to.

 

[Analog-1]

You could try some Muriatic acid it eats rust for breakfast. Just google a good mixture of acid and water it wont take long. Maybe worth a try.

 

[NYEngineer]

https://por15.com/collections/fuel-tank-restoration/products/fuel-tank-sealer

 

[drtyler]

https://por15.com/collections/fuel-tank-restoration/products/fuel-tank-sealer

The inside of the tank needs to fairly clean and dry when applied, but that product is very good.

 

[JohnnyG]

This POR-15 sealer looks to be the ticket to me. I wouldn't skimp on it though, at the minimum, I'd buy a quart AND an extra pint in order to account for the baffle inside. Maybe even 2 quarts. You're only going to do this once, so make sure EVERYTHING inside is coated.
My MC tank was coated with "Red Stuff" (don't ask me) and some of it wasn't cured real well. It eventually all worked it's way out, but was a hassle in the carbs for a while.

I'd prefer a 2 part epoxy, but these newer coatings are probably better and cheaper. Your cleaning method seems to be sound, but I'd avoid a strong acid, they tend to eat metal too! Stay with it until it's clean and dry, and you'll be fine. If you're seeing very fine rust and not flakes, you will be done.

 

[paulo57509]

There was a time when radiator shops could clean fuel tanks. Once they're cleaned, you're now faced with leaking. This can usually be addressed with a sealer.

I've cleaned and sealed neglected motorcycle fuel tanks but nothing as large as a car fuel tank. This stuff has been around for +40 years:

https://kreem.com/fueltankliner.html

 

[Dave Sherman]

Thanks all, I think I'm staying away from muriatic acid. I'm sure it works well, but I don't want to mess up this tank as it's hard to find a replacement. I'm on the fence with POR-15; as JohnnyG pointed out, that baffle makes it difficult. I had good success with POR-15 in the Honda motorcycle's tank, but that was a much smaller tank and didn't have the baffle to contend with. Perhaps since the old sender is already trashed, I can use that to close the top of the tank while I'm coating with POR-15.

More importantly, how do I prevent the flash rust when I'm drying? I've already seen that while I can dry it out quickly with the heat gun pointed into it, but I can see the shiny spots turning brown as it's drying.

 

[Chris142]

You could try some Muriatic acid it eats rust for breakfast. Just google a good mixture of acid and water it wont take long. Maybe worth a try.

That will start rusting again immediatly. by the time its installed its all back.

 

[JohnnyG]

Thanks all, I think I'm staying away from muriatic acid. I'm sure it works well, but I don't want to mess up this tank as it's hard to find a replacement. I'm on the fence with POR-15; as JohnnyG pointed out, that baffle makes it difficult. I had good success with POR-15 in the Honda motorcycle's tank, but that was a much smaller tank and didn't have the baffle to contend with. Perhaps since the old sender is already trashed, I can use that to close the top of the tank while I'm coating with POR-15.

More importantly, how do I prevent the flash rust when I'm drying? I've already seen that while I can dry it out quickly with the heat gun pointed into it, but I can see the shiny spots turning brown as it's drying.

I think drtyler is right. It needs to be "FAIRLY" clean, not pristine bare metal.

 

[KrisZ]

If you have a lot of rust, you will need agitation/abrasion to aid the rust dissolving solution. People use small washers, bearing balls etc and shake the tank every once in a while. For a car tank, you will probably need a second person to do that.

 

[Devo242]

I have used the POR-15 tank restore kit recommend it. The car in question is 40+ years old and had been sitting for over a decade with ethanol gas and it seemed like considerable rust at the bottom of the tank.

I thought the tank a write off but thought I would take a shot at restoring it before buying a new one which is available OEM. I used a garden hose to remove the hardened rust at the bottom and it came out in chunks, turns out it was some sort of hard formation that I can only guess what it was but when removed it left behind was something I could work with.

The full POR-15 kit worked well and I am happy with the results, attached a few photos: the Cleaner/Degreaser step was used once I had completed hosing out the bulk of the sediment and the jug shows what it pulled out. The tank is after the full clean and then after the POR-15 tank coating step was applied and dried.

 

[Dave Sherman]

Thanks Devo, I've got the POR-15 complete kit on the way. I bought 20 gallons of vinegar, and it's been filled completely this time at an angle. The vinegar has turned a lovely shade of brown, so tomorrow I'll dump it and rinse, rinse, rinse with baking soda and water to get as much crud out as I can, and dry it quickly with the heat gun. Hoping the metal prep step of that kit will kill any flash rust and get the phosphate coating on.

 

[Dave Sherman]

Vinegar for the win! I think filling it completely and heating it with the halogen work light on it for a few days did wonders. Even got a spot that the Rust911 had left. After several rounds of sloshing with baking soda and water, got lots of junk out of it. Just some light surface rust, and the heat gun dried it out nicely. Amazon says my POR15 kit should be arriving today, so I can get this thing done soon.