A person can determine if the radiator needs flushed out by checking the color of the coolant inside. This is done by loosening the drain valve.
If the coolant has a brown tint, or has bits of rust in it, this indicates a flushing is needed. Another way to check is for car owners to monitor their coolant reservoir. If the fluid level fluctuates greatly throughout the day, this signals a need for a flush.
If rust builds up, the engine does not maintain a proper temperature due to poor coolant levels, or if the coolant is contaminated, it can result in severe engine damage.