A control valve system for a coolant includes an inlet through which a coolant flows into a water chamber. A plurality of outlets discharges the coolant outside the water chamber. A valve housing defines the water chamber which is fluidically connected to the inlet and the plurality of outlets. At least one rotary valve is rotatably installed in the water chamber. An actuator rotates the rotary valve. A controller is configured to control a flow rate of the coolant discharged to the plurality of outlets by adjusting a rotational angle of the rotary valve by the actuator. The plurality of outlets include a first outlet connected to a radiator which cools the coolant, and a second outlet connected to a reservoir tank which removes bubbles of the coolant.