May 292014

The cars left the factory with untreated fuel tanks and so rusting from within was quite common. I wanted to seal the inside of the tank but needed to ensure that it was not of the PVC type, which is susceptible to hardening and cracking due to the increased percentage of ethanol used in modern fuels.

The other issue was avoiding the sealer blocking the small vent tubes again. Initially I’d looked at hot-dip galvanising but, after this was discounted, it came down to a choice of tank sealers from either KSB or POR-15. These both follow the same three step procedure; de-greasing, metal preparation and then application of the sealant.

In the end I opted for the KSB Gold Standard sealant. Although, oddly, the quantities sold are aimed more towards the motorcycle market. The tank needs to be rotated and rolled during all three stages of treatment to ensure all the surfaces are covered, including the baffles. Therefore it needs to be sealed to avoid leaks.

I didn’t want to ruin the final cork gaskets and so made up some silicone ones, using the left over two-part silicone used to create the mould for the heater vane.

Making silicone gaskets Masking tape retained the silicone Fuel sender gasket

The cover plate with the tube down to the fuel filter could be masked fairly easily to stop it being coated with sealant. Therefore it could be used to seal its hole in the tank. However the fuel sender couldn’t be masked effectively. So, to coating the moving and delicate parts, an aluminium disc was knocked up as a replacement.

Sealing the filler neck was slightly trickier as I couldn’t get hold of a large enough bung. A replacement bath plug from B&Q just about did the job, requiring some additional help from duct tape.

The KSB tank sealer is reasonably fluid which allows it to cover the internal surfaces fairly easily. As a result I concluded that periodic blasts of compressed air would be sufficient to stop the internal ends of the vent pipes from blocking.

Compressed air to clear vent tubes Sealed tank with de-greaser and metal prep Finally the sealant is applied

The first stage involved applying a warm diluted solution of KSB’s AQUA product to thoroughly degrease the tank. The tank then needs to be rinsed and completely dried throughout before applying their ‘Rust Buster’. Again, this needs to be rinsed and the tank completely dried before moving on to the final stage of applying the sealant.

The AQUA and Rust Buster are essential just a branded degreaser and a phosphate acid solution, to convert any surface rust. Therefore cheaper alternative options are available for these steps.

The Gold Standard tank sealer was then be poured into the tank and the tank slowly rotated to ensure all the surfaces are covered. A slow methodical approach to rotating the tank was definitely better than trying to shake the tank. The curing process doesn’t start for at least 30 minutes when it slowly becomes more viscous so there is plenty of time to get good coverage.

Compressed air was periodically blasted down the vent tubes to stop them blocking as well as every time the tank was turned. After about 30 minutes the unused sealant was drained from the tank before it started to thicken due to the curing process.

All surfaces need a light coating Draining the excess tank sealant Repainting the exterior

Unfortunately the various seals weren’t water tight so some phosphoric acid escaped over the painted exterior finish. The weak acid left light run marks in the paint which could probably have been polished out but I decided to repaint the tank with some POR-15 gloss chassis paint.

The completed tank sealed and re-painted

  One Response to “Treating the fuel tank”

  1. I have enjoyed following your project as I am doing a 69 2+2. You will need decals, one of which is the Crimson brake fluid decal on the firewall. SNG has not started stocking them yet, they are very slow in picking up new products.

    In appreciation of your efforts, I would like to send you a care package of decals for free. I will need your shipping address.

    Dean Ritter
    Restoration Parts Manufacturing, LLC

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