clean a tank

[moog]

my tank has an oily residue from the petrol, which is now looking like a dirty surface rust, since i piped in car exhaust fumes so i could have it welded,
I want to whipe it off but of course can't get my hand in, i put some rag in there and used a long screwdriver to whip it & it comes off OK but its just a matter of being able to whipe it off.
i chucked a sock it there with a few pebbles in ( tied up ) and swished that around & it did it a bit, but i want it fully clean.

Has anyone got any ideas or tips, or know of a liquid i can use to clean it, i thought maybe caustic, but don't want to put anything in that wouldn't wash out properly with petrol afterwards.
Any help gratefully recieved
:)

[Matt]

Why the car exhaust fumes?????

[sharky]

The idea is to remove any fuel vapour that could ignite....
The method I have used many times is much simpler.
Drain tank, remove any taps, fuel level senders etc. Remove cap and shake out as much fuel as poss.
Then just light a long stick and ignite the fumes around the filler cap hole. All you get is a whoooosh and a burst of flame that dies down to a small flame until all fumes are burnt off....Just don't be peering in the hole when you light it ...or you will have a killer haircut[:0][:0]

try metho,or theres a product called Super Solve which is alcohol based i think(sure gets me pissed). maybe a good wash with dish washing liquid is all it needs????

[damo1]

cant you just slosh some petrol around in there then empty it out and put a bit more
in then tip it out then a bit more until you get it clean every time you tip it out
it should take some of the shit with it.