Sorry to read your tale of woe. I once fitted a cooler to an LS430 which seemed fine for several months, but after a while I changed it for a new radiator thinking the original setup has to be best. The only thing that causes this "potential" problem is corrosion as the connections and washers aren't stainless. Corrosion causes the O rings to no longer seal correctly. The thing to remember is that this corrosion takes several years, if it happens at all, so I would (and am) be happy with just a new radiator and fresh coolant. Having seen your lovely Celsior I'm very pleased that it wasn't terminal!