A novel deionization filter for removing ions from a coolant in an electric fuel cell vehicle cooling system is disclosed. The deionization filter includes a filter housing having a coolant inlet port, through which the coolant enters the filter housing; and a coolant outlet port, through which the coolant exits the filter housing. An ion exchange bed having positively-charged and negatively-charged ion exchange resin beads is provided in the filter housing for removing negative and positive ions, respectively, from the coolant. At least one filter assembly is typically provided in the filter housing for filtering particles from the coolant.