I pulled the tank on my 71 Barracuda in order to clean the inside and remove the varnish and ethanol residue. I was hoping to find someone who could clean the tank without harming the lead- tin plating of its terne steel construction. Because the car has been in the family since 1971 (purchased with 13,000 miles on the odometer), I wanted to keep the original tank....especially since it first appeared to be in excellent condition with zero rust and no dings or dents. I attribute its condition to the fact that the car was garaged kept for most of its life. However, while removing the residue left from the top felt pad, I discovered a very narrow 8 inch line of rust-through. Any ideas why the tank would deteriorate in such a way at the top rear section of the tank?

Thanks,
David

What is the residue you are talking about? There should not be any residue. Whatever it is I bet it created a moisture barrier.

It looks like the area that comes in contact with the fuel tank support on the underside of the trunk floor. My bet is simply that some moisture was trapped in that area that was not able to evaporate. Probably some road salt mixed in too. We see strange thing disassembling these cars. My 1968 Dodge Charger 32K miles from southern California had rust in one spot, right on the corner of the windshield on the passenger side. Who knows? Didn't make any sense at all.

It looked like glue residue...as if a portion of the felt pad was glued to the top of the tank. I may be wrong. Or it may be that the pad deteriorated to the point that it turned into a sticky substance.

Are you sure it’s not rusting from the inside out? The ECS is right up there in that area. I bet it rusted out because of that.

I spread open the rust-through at one end of the crack and used a Maglite to look inside. Looks like you are 100% correct. The ECS upper chamber appears to be corroded. I would never expected to see a problem there. Usually you see issues on the bottom of the tank at the lowest point where moisture will settle. I will install a new Spectra tank for now and try to clean and repair the original later.

Auctually, its the top area that is more prone to the rust. It is exposed to the air AND the moisture. My oem ECS tank rusted out in my cuda when it sat for about three years with no use.

That looks like it started as a stress fracture to me.

Did you repair (possible?) or replace?

That’s not a stress fracture. No gas will get into the ECS area so all you will get is fumes and lots of rust. Mine was not rusted through like yours and still it was not repairable. It can’t be fixed, sorry. Using that tank would be about like rebuilding your worn out engine and reusing the worn out oil pump and destroyed rod bearings. Don’t do it. Get over the fact that it’s the original tank and toss it for a new one. I had another tank from a car I had parted out years before. Just buy a new Spectra tank and be thankful they make them again for a car that is 50 years old.

Fastmark, I apologize for dragging out this thread. But, I have one last question. Your eom ECS tank that rusted out after three years....Was the fuel that you were using 10% ethanol? If so, do you attribute the rust problem to the E10?

No apologies needed. That’s what this forum is all about. 👍 Mine rusted out long before ethanol was forced on us. I think it was in the mid 90’s. It sat while I did some work on the engine compartment and rebuilt the motor and trans. Mine did not rust through like yours, just completely rusted on the inside. It only had a 1/4 tank of gas in it for 3 or 4 years. I’m dealing with the same issue on a friends car right now. Restored the car using a cheap tank with no galvanized coating on the inside and it has sat for 8 years. It rusted the entire inside of the tank from methanol. Have to drive them and put stabil in them.

David,

The rust is from the lack of gas in the tank. If you had the tank full the chance of rusting on the inside is low. With little to no gas the rest is filled with air and depending on where you live determines moisture in the air. That leads to rust where you can get galvanic corrosion.

Still with fuel in the tank you should use things like Heet or Sta-bil to help reduce moisture in the tank if storing for any length of time.

my charger has sat since somewhere around 2006, with an almost full tank of gas. when this thing was first brought out of mothballs in 2000, [don't beat me too much ! ], the tank was really crusty, so i blasted the inside with sand, which removed the tern coating from the material, plus all the rust that was there. i put a large wix canister filter on the line just after it came from the tank. before use, i spent a BUNCH of quarters at the car wash to remove all the sand, and to make sure it was clean. that worked great, then it was parked again.
i just bought a stainless tank from vans, so when it sits again, HOPEFULLY, it won't get TOO nasty inside.
but, who knows ?