sporadic coolant smoke

[PlanZero]

Over the past year I've been having sporadic coolant smoke (also occasional oil smoke, but that's a different matter), sometimes worse than others. I have no loss of coolant, and a recent leakdown test shows my HG and valve seals are good. This only happens when I sit at idle for a few minutes. This is a 420a so turbo is not an issue. Any ideas?

 

[cdubb79]

Your head gasket may be leaking internally. Sitting idle causes the car to heat up faster. DO NOT USE ANY STOP LEAKS OR LIQUID COPPER. Keep an eye on your car's temp. As anything a little high may take it over the edge. Make sure your timing belt is still in good condition. One tooth jump and this would cause that as well.