The header tank for my engine cooling system is fabricated from 5mm mild steel and measures 13in x 10in x 3in.The inside is coated with rust - serious rust, flaking off in sheets. I've managed to remove quite a bit of it by rattling around through the filler with a mooring pin, but there is still an awful lot remaining, which will not be easy to remove because of limited access. I think the cause is due to the large size of the skin tank,which causes the header tank to empty as the engine cools and the coolant contracts, exposing the damp inner surfaces of the tank to the air.
My thoughts for dealing with the header tank were, after removing as much rust as possible, to empty a 500ml bottle of Fertan into the tank and give it a good shake to coat the inside. Once dry, do the same thing with Hammerite paint, which I have a few odd tins of.
I did consider cutting an access panel in the back of the tank, but I'd like to avoid this if possible.
Does anyone have any better ideas?