DuPont used to sell a 2-part powdered cooling system flush product that came in a double-ended cardboard canister. The active ingredient of the flushing powder was Oxalic acid. With the thermostat removed, the powder was poured into the radiator and the system was topped off with water. The engine was run for at least 30 minutes with part of the radiator covered with cardboard to raise the temperature to the normal operating range. Then the system was drained, refilled with water, and the neutralizing powder (baking soda) was circulated for 10 minutes. The final procedure was a 10-minute flush with clean water followed by a refill with the proper antifreeze/water mix.
The same thing can be done by using "Rust-Mort" or one of the other Phosphoric Acid rust busters used for body metal prep, followed by a box of baking soda dissolved in water as a neutralizer. I used Muriatic Acid (technical-grade hydrochloric) for radiator flush when I worked at a concrete plant. The cooling systems of our concrete mixers got contaminated with limestone dust and Portland cement pretty regularly, and we had big drums of the acid sitting around for cleanup purposes. Worked great!
Jerry
Last edited by Hotrod Lincoln; 02/11/2014 3:45 AM.
