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How to clean a 30 year old gas tank

bwright002

Active member
Joined
Feb 12, 2005
I just bought a 72 142s that was last on the road in 1990.
The tank has a drain hole, so I can empty any remaining liquids from the tank, but what can I use to clean out the varnish and whatever is left in the tank?
 
That depends on if there is any rust in there or not. If not, I’d just use any organic solvent like odorless mineral spirits. If yes, then you got a fun project I can walk you through.
 
Vinager works as well. Just dont let it dry out as it will reflash with rust. Leave it in overnight and let it do its thing. Just be aware if it removes metal and or corrosion you may end up witj some pinholes. Depends how corroded it is in there though.
If its gunky drain it let it dry out then toss a bunch of nuts bolts nails screws etc in there to scrape the loose stuff away. Then use a cleaner after that. Can use a vacuum cleaner on the blower side to check for pin holes later with some soap solution.
 
Guarantee you will get tired of rolling the tank around and your back will hurt.

This. If I had to do it again, I’d wrap it in a cheap camping hammock tied taught between two trees to make it less effort to shake and roll it.
 
I have used a carb cleaner that comes in a 1gallon can, made for dunking the carbs in to get rid of the built up junk. I also throw a hand full of small bolts in also. Pour in the clearer/ bolts let it sit / shake/ turn tank /repeat, do the for a day or so. Drain / use a magnet to remove the bolts flush with some gas/ drain. Have had good results.
 
Radiator shop is easiest.
"The Works" toilet cleaner, vinegar, muriatic acid, DIY methods also work but are dangerous and time consuming.
 
I took my old varnished up tank to a radiator repair shop. They cleaned and coated the interior for $90.

yep. I think mine may have been as little as $70

Best way by far. Get the radiator cleaned out while you're there too!

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I vote for the Rad shop option if you can find a rad shop that still does this.

Where I live the rad shops no longer offered this service. As others have suggested, I ended up using the POR 15 tank kit and 5 years later it is still holding up. If your tank is nasty pre abrade it using the nuts and bolts / whatever small sharp objects you can find method to remove heavy scale and surface contamination. Flush that out with regular mineral spirits before starting the POR 15 process. You may want to purchase an extra bottle of the POR metal prep if it is bad (parked for 30 years with gas in it is probably going to qualify as really bad). Be aware that when the POR tank sealer sets up, it is rock hard. If it sets up in threaded ports or the fuel suction tube you are screwed. After doing the coating process you need to clean out all the openings in the tank before the sealer completely sets up. Having an air compressor to blow out the suction line really helps.

Really look hard for a rad shop to do this for you.
 
The people who are fans of the molasses rust removal treatment buy the 1-5 gal pails of animal feed molasses. They also have lots of patience because if you have significant rust the molasses treatment is slow - like molasses in January. Allow a week or two for significant rust. The other nasty is that animals are not the only thing that feed on molasses. Under the right conditions microbes love it and you can generate a fine mold farm with a 'something died' fragrance. If you luck out some wild yeast might take up residence and they feed on the molasses and generate ethanol. Not sure I would want to try filtering the residue for a post de-rust cocktail.
 
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Thanks for all the suggestions. There was one local old guy who did rad and gas tank boil-out, but unfortunately he decided to retire earlier this year. I'm on the search for another such service. If anyone in West Michigan has a tip about a likely shop, I'd appreciate it.

In the meantime, I've removed the tank and started the removal process of rust. There was absolutely no liquid in the tank (given that it was last on the road in 1990, that's not too surprising). Haven't done the nuts, bolts and agitation process yet. Emptied out about a cup of rust by moving the tank around after blowing then vacuuming with shop-vac. Then a simple rinse out with some kerosene, drained it out through the small drain plug on the tank bottom, then dried it out with shop-vac blowing for about ten minutes.

Are the fuel level senders still available? Mine has a decent enough float, but it looks like the windings on the rheostat are broken. No idea if it will register anything when I get the tank reinstalled.

Also, on the bottom of the tank there's a small drain plug. Removed that one with no issue. But there's a larger brass opening, which I assume is where you get access to the in-tank filter. The fitting has a square female indent that looks to be just about 11mm or so (yes, I know the 140's didn't use metric for much). Anyone know what tool I'd use to fit into this opening and then gently work it open with my ratchet?
 
Now that you soaked everything in kerosene, you’re going to have to clean that out with a solvent before any acid will work. You won’t be able to remove the rust without some type of acid (hydrochloric, vinegar, phosphoric, molasses solution, et al).

11mm is pretty close to 3/8’s. Does the square drive on your 3/8s ratchet fit nice and snug?
 
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