Eric, if you go to your local auto parts store, there should be a section with various radiator products, among them "engine flush". They are usually alkaline (think detergent) based products mainly designed to clean rust, scale and other deposits out of the cooling system. They are not costly.
Years ago, I bought one from Prestone which included a special valve to install on a heater line; what this offered is a place to connect a standard garden hose and after you used the product, you ran water from the hose throughout the entire system. It's still available, called a "flush and fill kit".
Names of radiator cleaning products in the USA are those marketing by the usual gang; Wynns, Prestone, etc.
