brown liquid

[Bean]

that's unfortunately rather common on old engines like ours - over the years the lines inside the engine start to build some oxidation and rust... your radiator and water pump probably lookt the same... I have replaced my radiator early this year as the old one split and at the same time flushed the whole system with a pressure washer as good as possible and also replaced the tubes that go from the radiator to engine and back as these also had brown residue inside there walls...