[John_AZ]

Roland,
If you use this HD stuff your radiator may leak at the seam between the plastic side and the aluminum side. The next place the HD stuff attacks is a hose to metal connections on the engine. It eats the corrosion between the hose and metal. If this happens you will need to remove and clean all hose fittings, remove corrosion remaining and reclamp. Another part is the heater control valve. Do you see a chalky white deposit around the pivot? Replace if you do. It is leaking already.
If you think your radiator needs a more thorough flush, disconnect the hoses and back flush with water or like a poster above said, use a little TSP or quality dish soap.

Your experience may vary.

John_AZ