An engine cooling system is provided, which includes a water jacket through which coolant flows, a heat exchanger that cools the coolant, a bypass passage that bypasses the heat exchanger and recirculates the coolant to the water jacket, a first radiator passage that recirculates the coolant to the water jacket via the heat exchanger, a flow control device installed at a location where a coolant passage branches into the bypass passage and the first radiator passage, a second radiator passage that bypasses the flow control device and is connected to the first radiator passage, and a thermally-actuated valve installed in the second radiator passage. The flow control device performs a water flow control to adjust a coolant amount flowing into the water jacket by adjusting a coolant amount flowing through the bypass passage. The coolant flows into the first radiator passage through the second radiator passage, when the valve opens.