Petrol Tank Sealant

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MalcW
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Re: Petrol Tank Sealant

Post by MalcW »

So, just out of interest, what do cars use? A different type of metal? A specialist tank sealant? Do classic car owners have the same problem?

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Pharisee
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Re: Petrol Tank Sealant

Post by Pharisee »

Yes... Classic car owners do have the same problem. Not only with the fuel tank but all the related rubber bits in the fuel delivery system and carburettors.

Modern cars (and a lot of modern motorcycles) have moulded plastic fuel cells/tanks. Don't know which plastic they are made from but presumably, it's one that is not affected by alcohol.
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Rob Harknett
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Re: Petrol Tank Sealant

Post by Rob Harknett »

Reading all the comments, it does appear we have entered a new era of sealants & fuel. Not much we can do about fuel we are offered. So lets hope the new sealant's do the job intended with long life. Unlike sealants of old that soon gave more problems as a result of their use. Only time will tell.
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1608
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Re: Petrol Tank Sealant

Post by 1608 »

In the early '70s whilst waiting for the IOW ferry at Fishbourne, I discovered the petrol tank on my MGB leaking from rusty pinholes. I called the AA and the patrolman said there was nothing he could do but offer the following advice. "Don't mention or discover the leak till I was on the ferry and then put my foot down when on the mainland".
Not quite in the days when they saluted drivers, but still a practical guy on the motorists side.
A new tank cost £35.00 then.
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Pharisee
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Re: Petrol Tank Sealant

Post by Pharisee »

Are aluminium tanks any more or less prone to alcohol related corrosion?
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clanger9
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Re: Petrol Tank Sealant

Post by clanger9 »

It's not the ethanol itself, it's the acetic acid produced when the ethanol absorbs water and the bacteria get to work. Modern vehicles have sealed fuel systems, so the water absorption from the atmosphere is minimal.

Our bikes have "open" breathers, so there's nothing to stop moisture being absorbed from the air and the eventual production of acetic acid. This settles at the bottom of the tank and corrodes most metals (including aluminium). Some alloys are resistant to this.

As for why ethanol makes fibreglass go soggy, I think that's a different process where the alcohol dissolves the polyester resin...
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Stan Palmer
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Re: Petrol Tank Sealant

Post by Stan Palmer »

Hi Chaps, thanks for the information. The only sealant actually mentioned is POR 15 (unless I missed something). The reasons I want to use sealant have been well covered: corrosion under the tank and around fittings (tramlines in this case) which leaves thin metal and potential pinholes. Also, one tank had heavy dents pulled out. Pulling dents can lead to cracking later as the material is stressed at creases. Where this was most likely a braized layer was added, but you cant be sure. The tanks were tested for leaks using water and no pressure.
I don't use the bikes much: I do take the precaution of turning the tap off and running the carb dry, but draining the tank is too much of an imposition every time. It is under those circumstances that absorption of water is a problem. I should drain the tanks really: I end up throwing away the fuel in any case after a long lay-off.
I agree there are several different problems: the first is whether or not to use liner for mechanical reasons, the second is how to ensure it sticks properly, the third is how future proofed it is. I am not sure it is possible to fully cover the third: not possible to say how much ethanol will finally be in fuel. or indeed whether the boffins will come up with something even more problematic. 'Fit for Purpose' doesn't seem to come into it, they wont care if more modern vehicles start to fail, let alone older ones, if somebody can make a buck in the name of 'green policy'.

I will speak to a supplier of POR 15 and try to pin down the pre-treatment recommendations.
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JimFitz
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Re: Petrol Tank Sealant

Post by JimFitz »

Hi Stan

I recently had my Sunbeam tank resprayed and when my painter stripped it he found some filler on the top with some pinholes beneath. He had it welded and used Tapox liner which he uses regularly on all tank jobs. It is supposed to be ethanol proof but who knows what percentage and how long it will last. I will update in 20 years :lol:

As with all tank sealants, the finished job is only as good as the preparation.

Jim
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oldsmokey
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Re: Petrol Tank Sealant

Post by oldsmokey »

I used For 15 on my Model 31 in 2012 and it's never had an empty tank since. Everything is still fine and dandy.
I used Kreem on a Harley chopper that I run with a tank made from a narrowed BSA Bantam tank and it's been fine as well.

With both systems, it's all in the preparation. If you try and apply it to an unprepared surface it will peel off like a sheet of cellophane.
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Re: Petrol Tank Sealant

Post by MalcW »

Just a thought: If you have a motorcycle laid up over winter, would it be feasible to fill the tank and put something over the filler before replacing the cap - clingfilm, or something similar. I'm thinking that if moisture can't get into the tank, the fuel can't absorb it? At other times, when the bike is in use, if the fuel is used and replaced frequently, would that help, on the basis that it isn't in there long enough to absorb much moisture?

Or am I being ridiculous - it wouldn't be the first time...

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