Currie also recommends that during a complete flush and fill, you take advantage of a radiator flush product to help remove any heavy rust or scale deposits.
"These deposits can dramatically restrict coolant flow and reduce heat transfer, which may lead to your vehicle overheating or breaking down."
In a product like Prestone Super Radiator Cleaner, a super chelating additive effectively removes heavy rust and scale deposits by drawing metal oxides into solution. Though strong enough to help restore maximum cooling system efficiency, this non-toxic, non-acidic product, if used as directed, is easy to use and safe for all cooling system metals.
More information is available online at www.prestone.com.