How to clean gas tanks

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Tim Ko

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Re: 85 Chevy K30, 454, dual gas tanks, carb. It's a great truck.

Hello All,

I just getting back to starting it up. The last time I started it was about 10 years ago. I remember I dumped 5 gallons of gas in one of the tanks, new battery and vroom.

I assume there is (was) some gas in there still. Maybe water ... who knows. So, I tried to suck gas out of the tank via the hose on the carb with a mityvac. Pulled a vacuum but didn't a drop of gas through the line. Again, I assume it must be the fuel valve is all gummed up. I have no idea.

I just got under there and tapped on the bottom of the tanks and they sound empty. I pulled the filler hoses off the tanks and stuck a hose down there and came up dry.

Can that 5 gallon of gas evaporate in 10 years? I thought there would have to be something in there.

???

So, my question is what is the best way to clean the tanks; without taking the tanks out of the truck? Can i dump some kind of cleaner in there to loosen any gum in there. Marvel mystery oil maybe?

I just want to maybe just dump a cleaner in there and let it sit for a week and then get that hose back in there and suck out as much as possible and then mity-vac the rest of it out.

That tank looks like its about 5 feet long and it sitting nose down on a little bit of a hill.

I'd really appreciate some ideas on how to deal with that.

Thanks a lot

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CSFJ

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I'd be more concerned about rust from condensation than varnished gas. It might be worth it to borrow a boroscope and take a look at the condition of the insides. You may need to replace them if there's any rust.
 

Charlie

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:welcome:
 

shiftpro

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Welcome to the site Timmy and a hellova nice truck ya got there.
If you really want to clean the tank, remove it and take it to the car wash. Better yet a steam cleaner. Your local machine shop (automotive) might have a steam cleaner.
 

Tim Ko

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No shortcuts ???

Several years ago I cleaned out a 750 honda gas tank with 5 gallons of white vinegar. That really did the job. Then I "POR"'d it.
It turned out pretty nice but it took a week and I had to dump the vinegar and wash it out and then refill with the vinegar and repeat about 5 times.
So, I'm thinking if I power wash it out, it will just re-rust. So, I'd have to POR it.

Thanks CS, I was just looking at borescopes on ebay. I'll do that first. See where I'm at. If it looks bad, go to plan B.

Thanks for the welcome Charlie. I appreciate that.

Well ShiftPro ... I was really trying to avoid even thinking about taking it out.
It's siitting in the driveway out front. I'm not too keen on spending a lot of time putting myself on display in front of all the neighbors.

Thanks guys for pointing me in the right direction.
 

rpcraft

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White vinegar is a pretty non agressive way to do smaller tanks. Seems like it would be a cheap way to do it now if you have time to wait, but then again it also depends on if your tank is in good enough shape to be plugged off and remain leak free.

What was explained to me was back in the day they would start with the tank before they even clean it and hammer on spots to make sure make sure it's worth it to even push onwards. Then they dip and fill it in something like phosphoric acid or an acid concetrated enough to work quickly but not so much as to burn through the metal (too much). Something similar to what powder coaters use for metal prep when they use a chemical finish. The acid strip would essentially scour into the metal and eat up anything organic (like rust and varnish) so afterwards they usually bang in spots with a hammer again to ensure the acid didn't tear into the metal too much. Once at that point they will rinse and flush it out and then block off all the openings and dip it in a tank of water and put some air pressure to it to test for leaks, at which point they will fix with solder and patch soldering. Afterwards they set it up to dry, usually with a torch or some kind of furnace, and once dry and cool they usually will paint the outside of it. if asked they will line it as well but most usually just leave it raw and if you keep the tank relatively full the fuel itself will preserve the finish of the inside of the tank

Now days I think the only place that might do it is a real radiator repair place but I think in many cases now the tanks are so cheap it's really more cost effective to replace and have a parts warranty on the tank, than a workmanship warranty on a 30 year old piece of metal that has been acid etched and is possibly going to crack and break (from being thin and fatigued).
 

legopnuematic

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Personally I'd drop the tanks and either replace them or if not too bad and just some gunk put a decent amount of clean pointy rocks and some fresh gas and shake them about for a good while, drain and repeat until clean. Replacing the tanks to me is less of a headache than trying to get away with a dirty old one that can clog the pickup tube and fuel filters. Not a bad time to replace the rubber fuel lines while you are at it since everything is easily accessed.
 

Camar068

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Craig 85

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The other thing to look out for is the fuel lines. My truck has been off the road for at least 10 years before I bought it. Both tanks were about 1/2 full and smelled bad. For me it wasn't worth spending the time on the old tanks. I bought 2 tanks and fuel senders. I still had some rust sediment show up in my auxiliary fuel filter from the cross over fuel line.
 

Tim Ko

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White vinegar is a pretty non agressive way to do smaller tanks. Seems like it would be a cheap way to do it now if you have time to wait, but then again it also depends on if your tank is in good enough shape to be plugged off and remain leak free.

What was explained to me was back in the day they would start with the tank before they even clean it and hammer on spots to make sure make sure it's worth it to even push onwards. Then they dip and fill it in something like phosphoric acid or an acid concetrated enough to work quickly but not so much as to burn through the metal (too much). Something similar to what powder coaters use for metal prep when they use a chemical finish. The acid strip would essentially scour into the metal and eat up anything organic (like rust and varnish) so afterwards they usually bang in spots with a hammer again to ensure the acid didn't tear into the metal too much. Once at that point they will rinse and flush it out and then block off all the openings and dip it in a tank of water and put some air pressure to it to test for leaks, at which point they will fix with solder and patch soldering. Afterwards they set it up to dry, usually with a torch or some kind of furnace, and once dry and cool they usually will paint the outside of it. if asked they will line it as well but most usually just leave it raw and if you keep the tank relatively full the fuel itself will preserve the finish of the inside of the tank

Now days I think the only place that might do it is a real radiator repair place but I think in many cases now the tanks are so cheap it's really more cost effective to replace and have a parts warranty on the tank, than a workmanship warranty on a 30 year old piece of metal that has been acid etched and is possibly going to crack and break (from being thin and fatigued).

Hello RP,
Your describing the POR product. They give you a bottle of degreaser ... you dump that in there and swish it around. Then you dump that acid wash whatever it is and swish it around and let it sit. Then you flush with water ... blau blau blau. Then dry it and all that. And then ... and then ... and then ... and then finally you dump the por "coating in there and roll it around the tank and coat the bottom and sides and top. I think its like $40 for a motorcycle tank.

I think maybe just throw 100 at a new tank. It is a pita and it takes a while and there are a lot of steps. Vinegar overnight does a pretty good job but you have to repeat several times to really get it cleaned out.
 

Tim Ko

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Personally I'd drop the tanks and either replace them or if not too bad and just some gunk put a decent amount of clean pointy rocks and some fresh gas and shake them about for a good while, drain and repeat until clean. Replacing the tanks to me is less of a headache than trying to get away with a dirty old one that can clog the pickup tube and fuel filters. Not a bad time to replace the rubber fuel lines while you are at it since everything is easily accessed.

Hey Lego ... yeah there is some wisdom there. I'm kinda thinking maybe just do it right. Just do the fuel system over ... new everything.

Otherwise, maybe, you put a bandaid on it and it runs and then a week, a month, a couple months later it doesn't run.

"You never have time to do it right the first time, but you always have time to do it over."
 

Tim Ko

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Worth it's weight in gold, if you can afford it go ahead and get the wireless version. I checked for 2/4 bolt mains. Paid for itself already.

https://www.amazon.com/gp/product/B06WRNGYXY/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1

Hello Camaro, this is definitively the way to go. Definitely wireless ... but gotta search to see what is the highest resolution.
I think you need the best clarity possible; don't know if 1280 is the max or if 1280 is good enough. The mirror on a stick and
a flashlight "tool" is what I was thinking before I saw your post. Thanks for that.
 

CSFJ

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One of the guys I work with picked up a boroscope from ebay that plugged into his android phone. Iirc he spent around $20. He brought it into work to show us, the resolution was rediculously good.
 

Camar068

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Hello Camaro, this is definitively the way to go. Definitely wireless ... but gotta search to see what is the highest resolution.
I think you need the best clarity possible; don't know if 1280 is the max or if 1280 is good enough. The mirror on a stick and
a flashlight "tool" is what I was thinking before I saw your post. Thanks for that.

Up close the resolution was great. Anything beyond a ft or two it started to get grainy. For what it's made for it's great.
 

rpcraft

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New Tank definitely gets my vote...


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