Additional heating smokes

My V50 2.0 D has already squirted 2 times like stupid. The first time I had driven a road track of about 60 km behind me. After that it started to smoke in the engine room. I thought that the car torched me. I called Volvo and they sent someone from the ADAC. He noticed that nothing was missing, but that the diesel additional heating just sometimes smokes when it had around 4 degrees +. His ADAC service car would have. Today I have brought a 40 km highway ride and then 10 km of road behind me. After that the same again. Today’s temperature again 4 degrees. So I don’t think it’s normal. Do you have similar experiences?