It's very difficult to clean a radiator at home. You don't have access to a hot tank and that's the best method for getting those calcium deposits cleaned out. Also, the radiator may need a rod out. That's where the shop removes the top of the radiator and forces a rod through the cooling passages to remove especially stubborn buildup.
Thus, I would recommend you do take the radiator to a shop. Anything else is just wishful thinking.
Last edited by Klutch; 12-10-2012 at 01:50 PM.