Abstract: A new and improved engine coolant filter for removing particulate matter such as scale and rust from an internal combustion engine cooling system, the engine coolant filter comprising a filter element wherethrough coolant fluid may be circulated, the filter element including a housing having an input aperture and an output aperture, the housing also having filter medium disposed between the input aperture and the output aperture wherethrough coolant fluid may flow, and a manifold installed in series with a pressurized coolant line, the manifold having an input port and an output port, the manifold being removedly connected to the filter element such that coolant fluid flowing into the input port is circulated through the filter medium then out the output port, the manifold also having an automatic clogged-filter bypass valve whereby an unacceptable pressure differential across the ports caused by clogged filter medium shunts the coolant fluid around the clogged filter medium, the manifold further having a vis