Rick's Free Auto Repair Advice

How to fix a leaking gas tank

How to fix a leaking gas tank yourself

You can fix some steel gas tank leaks with special epoxy putty

Leaks in steel gas tanks are usually caused by rust-through pinholes, a corroded seam, or large areas of rust on the top or bottom of the tank. You can temporarily fix small punctures and rust-through pinhole leaks using a special gasoline-resistant epoxy patching material. But you’re kidding yourself if you think epoxy patch material will permanently fix  rust-through pinholes or leaks in seams. Those must be professionally repaired by welding/brazing and sealer, or with a new tank.

images showing pinhole leaks in gas tank

Here’s an example of severe rust-through pinholes on the gas tank fill neck. The DIYer figured all they had to do was remove the hose, wire-brush the rust and then patch with epoxy. But look what the wire brushing revealed; 5 pinhole leaks within a 2″ diameter circle. This steel is severely compromised and is quite literally Swiss-cheese.

fixed gas tank leak

There’s no way this gas tank patch will last.

Which steel gas tank leaks can be repaired with epoxy?

• Rust-through pinholes smaller than 1/8″ diameter can be patched temporarily with gasoline-resistant epoxy
  • Leaking seams can’t be repaired with epoxy.

You can’t fix a leaking plastic gas tank leak with epoxy

Yes, I know the epoxy manufacturers claim their product works on plastic gas tanks. But here’s the thing about plastic tanks; plastic gas tanks expand and contract from heat and cold and they bulge when filled. Epoxy cures to form a hard rigid patch that doesn’t expand/contract or flex like the plastic gas tank. So those repairs often fail.

Instead of epoxy, plastic tank repairs must be performed plastic repair kitusing a matching plastic patching material that’s melted into the puncture. If you want to fix a leaking plastic gas tank yourself, you’ll have to invest in an automotive plastic repair kit that comes with a variety of plastics and a melting iron. Before you do that, check on the price of an aftermarket gas tank; it may be worth your while to replace it rather than repair it.

If you can’t buy a replacement gas tank, try a sealer

Rusted gas tanks can be renewed internally if

POR Fuel Tank Sealer

POR Fuel Tank Sealer

they’re otherwise sound. POR Fuel Tank Sealer gets good reviews and just one of the gas tank sealer products you should consider. Here are the steps after removing the tank from the vehicle and draining the fuel:

1) Remove any old sealer that may have been applied to the inside of the tank
2) Degrease the inside of the tank to remove any gum or varnish
3) Add POR Metal Prep to dissolve rust inside the tank and coat/etch the tank with zinc phosphate to promote adhesion
4) Clean with water and allow to dry
5) Add sealer and rotate tank to cover all internal surfaces
6) Drain off excess sealer
7) Allow the product to cure for the recommended time

©, 2022 Rick Muscoplat

Posted on by Rick Muscoplat

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