1986 SE with 10k miles on it. When I bought it in January 2017, replacing the fuel filter was one of the 1st things I did. I didn't notice anything unusual when I emptied the old filter, but I wasn't necessarily looking either.

By July 2017, I had only put about 400 miles on it. I pulled the gas tank to put a new sending unit in. The tank didn't look bad to me, though I could see a minor amount of surface rust inside. Out of an abundance of caution, I took it to a local radiator shop to be cleaned. But, I wasn't worried about coating it.

When I got it back, the rust I had noticed was gone. However, when I put my fingers in through the top opening and ran them across the top of the interior of the tank, I could feel stuff flaking off. As I looked at the bottom of the tank to see what flaked, it was rust colored. The guy said that this happened to the top every time he treated a tank, and he didn't seem to know why. I theorized that the chemicals probably hit the top enough to cause them to flake and be ready to dislodge, but not enough to make them dissolve. Regardless, I assumed it was negligible anyway and the strainer would catch anything that flaked down. Even as I installed the tank, moving it around, I could hear crap bouncing around in there -- obviously the stuff flaking off the top. But, again, I pushed through.

On a whim, I changed the filter yesterday for the first time since January 2017. I had put about 500 miles on the car since the tank cleaning back in July. The filter was full of rust sentiment. When I poured the contents into a jar, the gas looked like muddy water with a bunch of sand at the bottom.

So, while it is possible that the filter has caught anything that was left in the tank, I want to be sure. It is also possible that the crap in the filter was there from BEFORE the tank was cleaned, but my instincts tell me no; I think this is the crap that flaked off the top.

I will be pulling it back down tonight. This time, I want to do it "right" and get it totally clean and then coat the inside. I deduce it is "80%" there with the first cleaning.

Is there a kit that everyone recommends that will first get all the rust completely out, then use a prodcut that will coat the tank and keep it rust free permanently? The good news, I still have the original sender, so I could put a chemical in and seal it with that sender to allow me to shake it and turn it upside down.

[This message has been edited by USMUCL (edited 05-16-2018).]

I used Caswell tank sealer for my heavily rusted tank. https://www.caswellplating....as-tank-sealer.html. As recommended I dislodged the heavy rust particles that would flake, but it doesn't have to be super clean because it uses the rust to cling to. When cured, it was very tough and seems to be doing well so far.

quote Originally posted by da.slyboy: I used Caswell tank sealer for my heavily rusted tank. https://www.caswellplating....as-tank-sealer.html. As recommended I dislodged the heavy rust particles that would flake, but it doesn't have to be super clean because it uses the rust to cling to. When cured, it was very tough and seems to be doing well so far.

The flaking materials, I believe, is what I'm seeing eventually break and get to the fuel filter. Did you use the Caswell recommendation to put drywall screws in the tank and shake it up to dislodge the flakes? I would be worried that, with the tank baffles, it would be impossible to get all the screws out. Or, worse, risk breaking a baffle.

In the marine industry I’ve seen all sorts of stuff put into tanks to clean them of rust, but my favorite by far is medium sized sling shot balls, they roll around easily and they’re heavy enough to knock crap down and being balls they shouldn’t get stuck. Also in the marine field a lot of folks go with “POR-15” for rust treatment of pretty much everything, but they have a kit specifically for fuel tanks as well.

I just wonder, with the baffles in our tanks, if even those metal balls would be tough to get out. I guess if you counted them and made sure the same came out as went in . . .

My fuel tank was quite rusty. Once it was removed, I put a length of chain into the tank and moved it around to knock as much loose as possible, then flushed it with water. Then filled it with vinegar and let it sit for about 3 days. Emptied, did the chain thing again, flushed, set it in the sun to fully dry, then reinstalled.

I am not a fan of coating the inside of a fiero tank as the coating likely will not stick well to the plastic baffles and eventually flake off and float around in the tank.

If you drive the car regularly and top off the gas when you fill up (vs. just putting a few gallons in), then the fuel sloshing will keep the surfaces protected from further rusting. If you park the car for long periods of time, make sure the tank is full.

quote Originally posted by fieroguru: My fuel tank was quite rusty. Once it was removed, I put a length of chain into the tank and moved it around to knock as much loose as possible, then flushed it with water. Then filled it with vinegar and let it sit for about 3 days. Emptied, did the chain thing again, flushed, set it in the sun to fully dry, then reinstalled. I am not a fan of coating the inside of a fiero tank as the coating likely will not stick well to the plastic baffles and eventually flake off and float around in the tank. If you drive the car regularly and top off the gas when you fill up (vs. just putting a few gallons in), then the fuel sloshing will keep the surfaces protected from further rusting. If you park the car for long periods of time, make sure the tank is full.

Hey, the chain thing isn't a bad idea . . . at least you won't lose it in the recesses of the tank. Were you concerned about the chain breaking the baffle when you sloshed it around?

So, I pulled the tank down. It didn't look bad, though I could see a little more of the junk at the bottom. The strainer was not stopped up like I thought it would be. With a mirror, I could see LIGHT surface rust along the top of the interior, which extended a few inches down the side. But, no flakes that I could see. Bottom line, I don't think the shop that treated it actually turned it upside down to get to the top. The stuff that's there likely just "sprinkles" down a little at a time and gets caught in the fuel filter.

The shop told me they'd "make it right." However, they were reluctant to coat it with the interior baffles, cause it the Red-Kote doesn't like plastic (they claim).

Instead of bothering to even take it back, I ordered the Caswell recommended above. It advertises that it seals metal and plastic, and that it sticks well to rust, so I think (hope) that it will be an easy fix and then I'll be up and running worry free for another 32 years

Will report back.

[This message has been edited by USMUCL (edited 05-17-2018).]

quote Originally posted by USMUCL: Hey, the chain thing isn't a bad idea . . . at least you won't lose it in the recesses of the tank. Were you concerned about the chain breaking the baffle when you sloshed it around?

Not really worried, the weight of the chain the gentle sloshing worked. Probably sloshed it for an hour as I focused on the various sections of the tank.

A few years ago I actually found locally a company that did gas tank repair and sealing, worked great, might be able to find something similar locally?

https://www.coilsradiatoran....com/gas-tank-repair

My tank was a rusty mess inside! I used POR to seal it. Here is a direct link to post in my build thread on how I cleaned and sealed my tank. 3 years later and all is well.

For reference, here is a BEFORE:




and AFTER:

For those of you with experience:

A shop near me cleans and coats fuel tanks so I dropped it off.

I also have some corrosion on the fuel pickup tubes that hold the float and fuel pump. It is not excessive but if I clean off the crusty stuff is there a paint I can use to coat it or just leave it bare metal? It looks like some zinc type stuff was on it before.