I am restoring my '80 Vette and found a problem with the gas tank. The inside seems OK, there is a sort of plastic liner inside which looks allright beside a very small crack:








But the outside has a problem, a lot of pinholes where it is rusted through:







I want to repair this without buying a new tank. I do not think the tank is leak because the internal plastic liner seems to be OK and the fuel tank was always filled with gas and i never found a puddle of gas or a bad gas smell in my garage. Pinholes this size should drain a full gas tank in an hour so if it was punctured i should have noticed i guess.

There seems to be a lot of clearance between the plastic liner and the steel tank, you can see the gap in the pictures of the pinholes so it looks to me the plastic liner is not touching the steel outer shell. Seems like moist has found its way between the liner and the steel outer shell and rotted through the bottom of the steel tank.

What are my options?

Weld the pinholes? Not my favourite, welding needs a clean part without rust and the damaged area is the most lower part of the tank so there is more rust on the inside. Also welding puts in a lot of heat which can damage the plastic liner?

Solder/braze the pinholes? Could be done maybe. The heat input is not so big and it needs only a clean outer surface. A big maybe...

Fill with Epoxy? Epoxy resin should be fuel resistant (Tank Cure is an epoxy resin) so i could fill the holes and the underside of the gas tank with a good epoxy resin. Should that do the trick?


Any advice on this one guys?

 

Looking at the photos, the pin holes are the results of rusting from the inside out. I would think that with that much rust on the inside the structural integrity of the tank is in question.

 

Well after more thorough investigation i am quite sure the tank is made out of a thick one-piece plastic inner tank surrounded by two half steel shells who were roll-welded together. I don't think a few pinholes will decrease its integrity but that is my personal opinion.

I have measured the inner lining distance to the steel shell which is at least 5-6 mm or more (almost 3/8"-1/4").

I would like to tip the tank over with the pinholes on top and just fill the entire space between steel and plastic with epoxy resin.

This bonds the steel and plastic together with a solid material which is gas-resistant and will completely fill the cavity between the shells so no oxygen is able to enter, thus stopping any form of rust. Also the resin will bond to a rock-hard solid so the tank will become even stronger if integrity was somehow in jeopardy.

After that i can sand and respray the tank.

Off course i will let the tank sit filled with gas for a few weeks or even pressurize it.

Any thoughts on that?

 

I had a similar situation with my '78. Tanks did not have any pinholes in it however. But in moving it around for a few months I dropped it on a corner ( during the winter when everything was cold) and somehow put a crack in the corner or the plastic. Not sure if there were other cracks since I couldn't see inside as good as you did. I thought about it a lot, maybe it could be repaired.But in the end, since I knew how much work it would be to drop the tank in the future, and not wanting to risk a leak and therefore a fire, I just bit the bullet and bought a new tank. +$200 seemed like good insurance. Just my $.02

 

That is absolutely the best choice, and if i was able to buy a good tank for $200 i would not hesitate one moment.

Problem is i live in Europe and good gas tanks are very rare to find. And if i find one the price will be at least double the amount you payed for yours...

So for the price of a set of good epoxyresin i am willing to take the chance. If it doesn't work so be it, the tank will be ruined anyway so i have nothing to loose beside a saturday replacing the tank for a good one.

I will pressure-test the tank after the epoxy repair and will have it sit filled with fuel for a few weeks to see if it is not leaking anything, i don't even want to smell gas in my garage.

I am driving without a spare tire carrier so i can check the bottom of the tank quite easily when assembled.