Hi, Obviously I can't say it isn't a head gasket but I have owned vehicles with the same engine for years and used to read forums a lot and there was never really much mention of head gasket problems that I recall. First step for me would be a compression test. How bad is the coolant loss? Have you been topping it up a lot? White / Grey smoke could be unburnt diesel or possibly oil from the turbo as well as coolant. Clear dripping water could well be normal if from the air con system. I can't remember exactly where it drains from off hand though.