Fiat Chrysler is recalling almost half a million Ram heavy-duty pickups and medium-duty trucks because their water pumps could be defective. The recall involves Ram 2500 and 3500 pickups and Ram 3500, 4500 and 5500 chassis cabs from the 2013 to 2017 model years. All 494,417 of the vehicles involved have 6.7-liter engines. Most of the trucks were sold in the U.S., but 46,220 are in Canada and 4,485 are in other markets. Fiat Chrysler says a water pump bearing can overheat under certain conditions, potentially leading to an engine fire. The company isn’t aware of any injuries or accidents related to the defect. It no longer uses the type of water pump involved in the recall. Fiat Chrysler will notify customers and dealers will fix or replace the water pumps for free.