I'm not into those cleaners. I have used them and had water pump seals go in the next 100 miles or so. Related? I doubt it, but my feeling is that if your system was well maintained then you don't need it and if your system was so neglected that you got lots of crud...well I doubt the stuff would get that much out anyway.

I guess I would use a cleaner right before I replace all the cooling system parts, (pump, stat, hoses, radiator, etc) to maybe clean the block and head a bit.

I don't use Volvo coolant. Only the orange dexcool extended life. They will work great in your Volvo. But make sure you get all traces of the old coolant out. Use a good water rinse, button it up with only water start the car and drive a little. Repeat rinse. Then force the last water rinse out carefully with a compressed air rig.

It's not that the orange stuff is not compatible with green coolant, it's that you lose some of the properties that make it last forever when mixed with other chemsitry, so basically it's like a "normal" coolant.