I put a date as I had no choice but this has been a gradual process and is endemic in cars where the water is hard. The solution is to fill your radiator with soft water or spring water or even distilled water (plus obligatory anti-freeze ) if you live in a hard water area.Modern antifreeze btw inhibits corrosion and helps prevent the problem Great cars Dodge Caravans, cheap, tough and dependable but subject like any mass produced vehicle to the vagaries or environment and lack of attention.