3rd Rusted Fuel Tank Cap in 1 year.

[Dasgog]

Hey

So 2-3 years ago I replaced my fuel tank with a brand new one. I also did the fuel filter mod from 3 canister filters to 2 spin on filters. I replaced the fuel lines [all of them] and even rebuilt the IP.
I verified, both ends, that I have free flow on the pressure line[?] from the tank to where it connects to the exhaust pipe.
The tank itself has no rust, but each cap, underneath, is like insane corroded rust!!! Is there like an additive I can put in the tan in case there are debris of rust or even spray the bottom of the cap so rust does not form? I will get an additive I need if need be.
I am in Arizona, we, uh, don't do rust. Ya know? So I am very confused.

 

[Mullaney]

Hey

So 2-3 years ago I replaced my fuel tank with a brand new one. I also did the fuel filter mod from 3 canister filters to 2 spin on filters. I replaced the fuel lines [all of them] and even rebuilt the IP.
I verified, both ends, that I have free flow on the pressure line[?] from the tank to where it connects to the exhaust pipe.
The tank itself has no rust, but each cap, underneath, is like insane corroded rust!!! Is there like an additive I can put in the tan in case there are debris of rust or even spray the bottom of the cap so rust does not form? I will get an additive I need if need be.
I am in Arizona, we, uh, don't do rust. Ya know? So I am very confused.

.
Dissimilar metals.

Aluminum tank, brass cap - and a cap with 4 little metal circles on the top of the cap.
You can get after one of the old caps with a with a wire brush until it shines. Then coat the inside of the cap with a light coating of RTV or something like it. Let it dry for a week or so, then replace what you have and see if that solves your rust problem.

 

[Dasgog]

Roger that, I shall give it a go. TY.

 

[Guyfang]

I don't seem to remember brass caps. Or not in the old days. Is this an A2 or A3? The A2 had a non brass cap. And when I looked up the cap tech data, it said ANY acceptable material. I seem to remember steel.

 

[Dasgog]

I am sorry, 1972 M35A2.

 

[ToddJK]

Perhaps the diesel fuel has had a little higher content of water in it, diesel will absorb water into it unfortunately. Does your new spin filters have water removing filters and if so, are they drained every so often? Only suggestion I'd have is add a couple bottles of Heet to each tank of fuel and see if that helps keep the rust down as it converts the water into methanol and allows it to burn witht he rest of the fuel.

 

[Guyfang]

I used this type fuel tank cap on trucks and gen sets, in Germany, where its wet all the time, and the caps got rusty. I used the caps in Ft. Bliss, where the humidity is low, and rain is like hens teeth, and the cap got rusty. Its a problem with water in the fuel. The CECOM and TACOM both told us, keep the tank as full as you can when not using the set. Less air in the tank, and it wont rust as fast. I think that is horse hocky. No matter how full it is, there will always be water in the fuel, and air at the top of the tank/fuel fill tube. We just replaced the cap, when the air inlet valve on the cap stopped opening/closing. There has got to be some kind of coating to use on the underside of the cap.

 

[msgjd]

On trucks & equip that sit a lot, I coat their caps with a very light coat of GAA.... "Goop, Automotive & Artillery".

 

[87cr250r]

You could add a volatile corrosion inhibitor to the fuel tank.

Vpci-326™ Corrosion Inhibitor Oil Additive 32 Oz | Aircraft Spruce

Vpci-326™ Corrosion Inhibitor Oil Additive 32 Oz An approved Lycoming engine oil additive for prevention of oxidation of all metals. Designed for use in engine oil at 1:10 concentration, VpCI (Vapor Phase Corrosion Inhibitors) wil

www.aircraftspruce.com

 

[Dasgog]

Hey guys sorry about the delay. Been in the hospital twice in past 3 weeks and no one knows what wrong. Just haven’t been motivated to do much, but didn’t wanna sound ungrateful.

 

[simp5782]

You can coat the inside of the cap with prune spray found at lowes. Let It harden before reinstall and no more corrosion

 

[glcaines]

I have a 1998 M35A3 and the cap spring was very corroded when I obtained the truck from Sparta. I cleaned the rust off and covered everything with grease. It immediately corroded again. I replaced the cap with an NOS cap that looked perfect. I again coated the spring and everything on the bottom of the cap with grease. Within one month everything was corroded again. Actually, the aluminium cap itself isn't corroding, it is the steel components, and especially the spring. They should have used stainless steel.

 

[Dasgog]

Honestly I just am surprised no one has made a more modern plastic one like every other vehicle. But, I mean, whatever.

 

[87cr250r]

It needs to be coated with something not soluble in diesel fuel. I'd try soaking it in some engine coolant first.

 

[Dasgog]

Well I have 4 coatings to look into

 

[87cr250r]

You can also use a battery charger and some zinc to galvanized it.

 

[Dasgog]

Well, prior to this conversation I bought my 4th Gas Cap so it gives me an opportunity to cure it before any fuel Exposure. I also bought golden zipper boots to replace cause imma tell you this, I ain’t ever taking those wheels off and knuckle this and that and all that BS. Not for boots again. I EARNED my zipper boot method.

 

[Dasgog]

You can also use a battery charger and some zinc to galvanized it.

I was just curious, how does one connect a positive and a negative to the same piece of metal without killing themselves?

 

[Dasgog]

I am revisiting [i guess i never resolved] this topic because, ok yeah cool I think I have the cap situation resolved and then I got 2 new filters BOTH with drains and am doing that, but now unfortunately I see the rust has gone down the inner sidings of the tank, just below where ya put the cap, so now the rust has "gone deep". I really do not know what to do here.

Really, I am debating on selling the deuce dirt cheap NOT because I do not love it or I can not do it, but I simply do not feel it is legit and healthy for it's well being to only start it, drive it a mile once every 3 weeks. It is just sitting and going to go bad, but it has had nearly EVERYTHING done to it.

 

[Valley Rock]

You're getting crappy fuel, it more than likely is that vegetable oil mix Fuel and that vegetable oil attracts and retains water like a mofo .

This is what happens when you go to the fuel station and run that "perfectly clean" diesel in your old Deuce so that you won't have any problems, it's just the opposite .

If you haven't figured it out by meow, fuel nowadays is total crap, gasoline is even worse, it's made from corn which attracts water like nobody's business .

The fuel tank in my old Deuce is full right to the the top with diesel, used motor oil, and ATF, and I've never had a rusty cap, far as I know it's been on there since 1963 but I can't prove it .