The radiators are terrible for it we done a E39 on friday was the same wasnt pissing out tho only leaked when warm , the E46's also do it or the plastic bottle bursts on the side of the radiator but you know when that happens. Lucky you mate not a nice job as above to do a head gasket on these we dont do many, the engines are fairly bullet proof its silly things round about them that cause probs , coils,air flow meter,radiators or the heater resistor drains the battery all can be sorted fairly easy.