Yes, if you see steam, that indicates a leak from the radiator that should not be there. I recommend replacement before it gets out of hand and overheats.
That does not exclude the HG's though (Both radiator and HG's COULD be a problem). The HG's can leak from the combustion chamber into a coolant passage. I'm not telling you that they are bad - if you have no symptoms, than maybe not. Testing for hydrocarbons in the coolant is an excellent idea, though I have no idea how to do that.