Icky Sticky Goo...

I am fixing up a almost completely knackered Series 2 buggered in every way, the big problem is the whole fuel system was clogged up with what smells like old veg oil mostly now cleaned out but the fuel tank has an inch of incredible hard sticky gunge in it and the brass fuel and return pipes are blocked. Any ideas, boiling caustic soda may be ???
Cheers to all.

Take some sample of the gunge out and try mixing with different solutions ie Thinners , white spirit,parrafin, diesel to see what breaks it down the best then puts some nuts bolts and the fluid in and shake it about to help break it up.
You'll need to remove the tank.
Steam pressure washer may also help.

^^^^ When all the above is done consider cleaning with brick acid maybe overnight. Then a really good flush with water and be patient with the drying time before adding fuel.

Gallon of solvent brake cleaner from local motor factors

Thanks very much, the tank is off the chassis so I have good access but the gunge really does not want to come out. I'll be back working on it on Monday so at least I have some new ideas to try out, cheers.