Abstract: A self supporting-one piece resilient metal wire cloth filter having an integral and permanent bypass opening (window), the filter being removably disposed in the inlet duct of an internal combustion engine radiator. The filter can be removed, flushed, and reinstalled to remove foreign particles entrained with the liquid coolant as the latter circulates, thus permitting continued high efficiency of heat transfer from the hot cylinder to the coolant and from the coolant to the radiator core.