Different manufacturers recommend different intervals for flushing the coolant from a car's cooling system, but the most common time frames range between two to three years. This time frame varies with the particular vehicle and the type of coolant that the car needs.
A coolant flush involves removing all of the fluid within a cooling system. Hoses attach to both ends of the system, and the technician power flushes and cleans the whole system before adding a new mixture of coolant. Any dirt, rust and sludge that have built up go out with the old coolant, and the result is a healthier engine.