Cleaning the insides of old fuel tanks

[Keith Webb]

Just been working on one of the fuel tanks for the gun tractor and having managed to remove the fuel guage sender I can see the bottom of the tank is covered with a sludgy tar which seems to be very difficult to remove.
When I took the tank off there were several gallons of water in it. It appears to be sound though. Interestingly the brass float on the sender has been corroded. What sort of chemical compound would do this?



Can anyone suggest a solvent which might dissolve this tar?

For the time being I'm trying soaking it in fresh fuel overnight to see whether this will soften it.

Here's a comparison with a standard tank.

[Alex Blair (RIP)]

Originally posted by Keith Webb
Can anyone suggest a solvent which might dissolve this tar?

Hi Keith..
That sludge may be water soluable as opposed to oil soluable..Try an intense mix of water and washing soda..That will do both...
Scrape some into a dish and add soda and water and see what happens to the goop..If it softens or disolves it,make up a intense mix for the tank and let 'er soak for a day or two..
Hy pressure wash out the sludge.

Originally posted by Keith Webb
the bottom of the tank is covered with a sludgy tar which seems to be very difficult to remove.

Ah, Rory has this problem in the CS8 but not so bad; the CDSW tanks had gone from tar to crystalline green stuff.

A large quantity of acetone works well, dissolves almost anything, but you have to be convincing with the local chemist to get a couple of gallons.

I may have not remembered this correctly but I'll see Rory in a few hours and re-confirm; our local garage man and classic restorer says a mixture of No.1 paint thinners and white spirit works very well.

No.1 thinners to us is the very ordinary stuff we use for all synthetic paint, red oxide etc and gun washing, it is not the stuff for acryllic or two-pack.

White spirit was also known as turpentine substitute some years ago, I have no idea what the rest of the world calls it. http://physchem.ox.ac.uk/MSDS/WH/white_spirits.html

The other trick to clean dried fuel tanks goes like this. Get/borrow/hire your domestic size, one barrow, electric cement mixer.

Find an old car or its windscreen (toughened) (possibly two) and shatter it into those tiny squares. Collect the glass bits.

Fit/strap the fuel tank to the mouth of the mixer with bungey cords or whatever to the interior mixing paddles, fill with broken windscreen glass, switch on and walk away for the rest of the day.

Remove, empty and blow out with the airline.

R.

[Keith Webb]

I tried the caustic soda - which I think would work but be a pain to remove... I managed to get most of it out using boiling water, then while the tank was still warm (and the tar soft) a couple of washouts with petrol.
I hope to hook it up tomorrow to see whether it's OK.

I like the idea of the broken glass - just wear a mask when blowing out!