Classic cars forum & vehicle restoration.

[bob2]

Any suggestions on how to clean a petrol tank, its the tank of a 1969 fiat 124, it has small rust particles and debris inside and we need to clean it thoroughly.
My idea was either a big chain inside the tank with petrol to clean it all up or assorted nuts and bolts instead of the chain!!
However is there a need to seal the inside afterwards?

[MikeEdwards]

I've heard molasses is (are?) a good thing to use for cleaning out tanks.

As for sealing afterwards, I guess it depends on what the condition is like once it's been cleaned out. I'm reading about some of the traditional tank sealants not being suitable for higher Ethanol fuels, though, so look at that before you buy something.

[bob2]

We still have to take out the tank so not sure how bad it is but most probably its only surface rust in there so a good clean as I mentioned should sort it without any need to use any sealants!!
I would use molasses but the main problem is I do not know were I can buy it from?!
We're in Malta, maybe I can try some supermarkets but no idea what to look for actually!!

[ukdave2002]

I have a tank of molasses solution in my workshop, anything that is rusty gets chucked in, it takes a couple of weeks to work, but then any corrosion almost peels off is if it were a brittle layer of paint, the metal left is completely bright.

If you do use it for your tank, it will need 4 weeks with a fresh solution (takes a week or 2 for the solution to get going), drain the solution, let the tank dry,and then chuck a load of nuts and bolts and give it a good shake as you had planned, the rust will then break away very easily.

I use Lyons Treacle as my source of molasses its pretty cheap.
Here is an old thread about it: http://www.oldclassiccar.co.uk/forum/phpbb/phpBB2/viewtopic.php?t=4892&highlight=molasses

I did look up the chemistry of why it worked but it was beyond me

Dave

[bob2]

Thanks Dave had forgotten about that thread, will do this weekend and report back here after a week or two!!

[Kenham]

A good way to clean a tank of rust is to put some stones or nuts and bolts etc inside then tie it to a concrete mixer. Leave it rotating for as long as it takes to get it nice and clean. I usually count the nuts etc as there is always one that hides inside only to rattle when refitting to the vehicle.

[Jim.Walker]

28 years ago I built my Gentry utilising a used Triumph Spitfire tank.
Initially I had trouble with rust scale etc. and I suspended a magnet on a wire in the tank via the filler neck.
Initially I cleaned the collected scale off the magnet weekly, but after about a couple of months I threw it away. I have never left the tank dry and have never had trouble since with no further attention in well over 100,000 miles. With only petrol vapour and no oxygen rusting will not occur.
Jim.
_________________
Quote from my late Dad:- You only need a woman and a car and you have all the problems you
are ever likely to want". Computers had not been invented then!

[bob2]

well you are probably right Jim, but just to be safe we'll be doing the trick with the treacle and use a chain instead of nuts etc to avoid any remiaing in the tank.
the idea of the magnet is also a good one, maybe we'll include it at the very end to see whether there's any scales remaining, + we'll be adding a filter outside the tank ti save the pump this time if this should ever happen again!

[bob2]

On Saturday the petrol tank got taken out of the car and after unbolting the sender unit from the tank and bolting back a piece of plastic as a blank, we proceeded to fill it up with around 30 litres of diluted treacle and warm water!!
leaving it for 2 weeks now!!
It wasn't that bad on inspection so probably a chain inside and some flushing with petrol would have been enough but we decided on trying this out and see for future projects!!

[alec.elliot]

Hi there

I had a similar problem with my Morris 8 series 1.

I cleaned mine out using a strong solution of Soda Crystals and water, topping it up through the fuel sender hole (and sealing everything else off.

I then connected the negative of a battery charger to the tank and the positive to an "electrode" (I used a piece of 12mm studding) suitably insulated from the body of the tank, immersed it in the solution once again through the sender hole and turned on the charger. I had put a 21W bulb in the circuit and on turning on it glowed brightly but as the electrode got fouled up with the rust it would go dim. Take it out and clean it and then put it back in again.

See this link:-

http://www.realclassic.co.uk/techfiles/petrol_tank_rust_removal.html

I cannot see everywhere inside my tank as there are baffles but the areas I can see look good and clean after just a couple of days of this treatment.

Be cautious with the solution. (no exposed skin and wear goggles) and also dilute heavily once you have finished but its worth a thought.

I then dried it out thoroughly and "sloshed" the inside. So far(only a month) no problems at all!

Have fun.

Alec

[bob2]

thanks alec!! sounds like electrolyssis!!
the car was back on the road a couple of weeks ago, went for a couple of runs and its fine!