Neilsen CT2389 Engine Cooling System Cleaning MachineNeilsen Engine Cooling System Cleaning Machine According to the engine maintenance regulations. It needs to replace the antifreeze after driving 20,000 miles or yearly If you do not change the antifreeze for a long time. Then the engine will rest and scale up which is the most common problem with the cooling system. Rust and scale will limit the flow of coolant and also forms an acidic substance that corrodes the engine and may cause heating. The new