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MG TD TF 1500 - Fuel tank cleaning

The TF fuel tank was dip-stipped for paint which also cleaned her up pretty well inside, except for a trough of rust (about 1.5" wide" running the length of the bottom, which doesn't look that bad. The sides look clean except for a few splotches of rust. I found a local guy with a genuine hot caustic tank (NaOH) (very rare these days). I don't think the tank is bad enough to require a seal, but am wondering: after the caustic dip and water rinse and hot air dry, what to do next? tumble a quart of phosphoric acid to condition the metal? Coat inside with a light lube (WD40)until gas goes into it? I need to condition it somehow so flash rust doesn't start.
thanks,
Tyler
C.T. Irwin

Hi Tyler,
I used some diesel fuel in mine to prevent flash rust. The WD40 will evaporate too quickly. It's been OK for 4 months in low humidity, but I have not done along term test. Mike D.
MW Davis

After you have the hot caustic dip, why not seal and protect the tank with one of the gas tank sealer kits that are out on the market?
Gene Gillam

WD 40 is not a lube, but was designed for exactly what Tyler is suggesting - it is a water displacement treatment, invented to prevent rust on steal plates in storage. When it evaporates, it leaves a rather sticky film on the surface that it has been sprayed onto. Be careful of tank sealers, what works with todays fuels may not work with the fuels 20 or 30 years from now. I put a sealer in the tank of our TD when I restored it in 1980 and it worked great until about 5 or 6 years ago. Todays fuel formulation started dissolving it and dispersing it through out the fuel system, where it became a great glue to stick fuel pump valves and needle valves to their seats. I had to have the tank stripped (including paint) treated with a zinc phosphate solution and then repainted - close to $1000 by the time I was finished. Cheers - Dave
David DuBois

thanks Dave,
I'm trying to avoid coating the inside if not necessary. After decoating, did you do anything to the interior prior to filling with gas?
Tyler
C.T. Irwin

Am I wrong or has the ethanol in gas been found to break down the coatings in the fuel tanks?
Bob Dougherty

Tyler - The only thing done to my tank after removing the sealer was the zinc phosphate treatment. This treatment left a slightly rough (or toothy) finish that I was told would absorb the oil in the fuel and keep the tank rust free - I'll let you know how well it works in another ten years :-).

Bob - I have to think that the ethanol in today's fuel was the cause of the sealer failure, but there is no way I can prove it. With all the stuff they stick in the fuel today, it could have been anything. Cheers - Dave
David DuBois

I'll add my two cents worth here. Firstly, I would just treat the tank with a proper sealant. If you want to coat it in a rust preventing film temporarily, I would personally suggest biodiesel.

Biodiesel is remarkably different from diesel - it has properties very similar to WD-40 in that it is much more of a penetrant than diesel, (so much so that you need special hoses for it on a diesel engine, it will soften and seep around rubber), it is a much better lubricant than diesel (many people add it to regular diesel because it extends engine life), and it leaves a very even coat on any surface, thicker and longer lasting than WD-40.

It would, I think, be much preferable to regular diesel as a rust-preventer.

Geoff Baker

Well, after dipping the fuel tank in hot caustic, all the rust on the bottom disappeared, but several pin holes appeared.So, will have to go the sealing route after all. Ordered a Qt of Caswells (epoxy), wire-wheeled the flash rust off, and rigged this rotisserie (photo). Next, will follow Larry Shoer's method for prep and seal. Plugged the 2 bottom drain and fuel line holes w/ rubber plugs. Will plug fuel filler and float holes with big rubber plugs. Not sure how to protect the 6 tiny bolt holes of the gas float. Any better ideas out there?
thanks,Tyler


C.T. Irwin

I would suggest you have the pin holes brazed in before you begin the sealer.
LaVerne

Is there any reason you couldn't just fill the pin holes? It seems a shame to coat the tank for a few pinholes that could be welded shut.

Alex
Alex Waugh

Tyler,

I've been combing my brain for some additional hints.

For the gas gauge sender unit buy a solid electrical cover plate (Home Depot, Lowe's, etc.). A 4" solid or a round (check) plate should be fine. Using a paper template, transfer the hole locations from the tank to the electrical plate and drill these out. Fabricate a gasket out of appropriate material. Use Saran Wrap (or equivalent to make a sandwich of metal cover plate, then gasket, then Saran Wrap and place over sender unit opening. Secure with six original bolts. The Saran Wrap will prevent the epoxy from sticking to the gasket.

Similarly, I used two layers of Saran Wrap to isolate all rubber stoppers from the epoxy. (For any epoxy project, Saran Wrap is a good way to prevent epoxy from sticking.)

One concern about your rotisserie: I'm not sure that the epoxy will coat the tank sides well. I'm tall and agitated and rolled the tank by hand. I let the tank stand on its side for a minute or two and did this a couple of times to make sure the epoxy had time to thoroughly cover the sides of the tank.

Refer to my notes for the extended working time you can use to make sure the inner walls of the tank are well covered. It is considerably longer than the directions might suggest. Remind yourself of the orientation of the internal baffles and try to make sure you maneuver the tank to get good coverage of them.

When initially mixing the epoxy, don't just stir it in the mixing pot. After initial mixing, pour the epoxy into another pot and mix there, and maybe pour it back and mix in the first pot again. This stuff is quite viscous, which requires special effort to make sure it is mixed well. The advantage is that it really sticks and has good build on the coated walls.

If you have other questions, please let me know. I'll try to answer.

Larry
(who has been tied up in home remodeling projects for a couple of years)
Larry Shoer

Tyler, Eastwood makes some great stuff called "Metal Wash". It is in powder form and you just add water and wipe, spray, brush, or dip your freshly blasted bare metal parts and it prevents flash rust. I have been blasting parts off and on all winter and waiting for summer so I can prime with exoxy and then paint. I have only used metal wash up to this point and none of my blasted parts have rusted in any way.
Richard Taylor TD3983

This thread was discussed between 04/03/2011 and 21/03/2011

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