Why did you add coolant in the first place? If it was low, you might have had a leak before you added coolant.

Your cooling system has some extra space for air because air is compressable while liquid is not. In theory, your cooling system builds some pressure to make the coolant boil at a higher temperature. I do not know what the relationship is, but I think that it is about one degree per pound. If that is so, a radiator cap that holds 14 psi. would raise the boiling point of water about 14 degrees. This combined with other chemicals in your coolant might raise the boiling point of your coolant to 225 or 230 degrees.

If your coolant level was much too high, expansion might make your cooling system "liquid full". This combined with a faulty pressure cap on the system could, in theory, cause very high pressures to be generated in the "liquid full" situation. This excess pressure could cause leaks in your cooling system.

Can you tell if this cloud is coolant or water? If it is water, it could be the result of some sort of condensation, or an outside water leak - both are not too serious. If the cloud is coolant, you may have a serious problem.

You did not hear this from me, but sometimes you can taste the leakage - coolant has a sweet taste. (although I have never tasted Volvo coolant, and too much tasting can prove fatal!)
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2 8s & 2 7s 600,000 miles total