I have sprung a leak. No amount of nappies will stop it
Its coming from what appears to have bodged up before once up to temperature ( the black splodge )
Any way of taking that pipe off? if so is it just a rubber Oring sealing it?
If its the metal cross pipe then there is an O ring on the end and the pipe slips into the stat housing.. the housing looks like its farly new?? so the steel pipe should come out, you will prob have to take the pulley off though it may not slide out with that in the way.. if the pipe is rotten (common) not sure if they are available new still..
You may fond someone (do you know a plumber mate?) that could braze upo the corrosion, but its a bodge and likely to come back and bite you in the back side..