Abstract: The present invention provides a hydro-actuator thermostat system for controlling a temperature of an engine. The hydro-actuated thermostat system includes a thermal responsive valve system configured to induce opening of a temperature responsive valve upon an increase of a temperature of a coolant fluid, and to induce closing of the temperature responsive valve upon a decrease of a temperature of the coolant fluid. The hydro-actuated thermostat system further includes a hydraulic actuator system controllable by a controller, wherein the hydraulic actuator is associated with a thermal responsive valve system and configured to induce opening and/or closing of the temperature responsive valve in response to an indication from the controller, the opening and/or closing of the temperature responsive valve may be performed by controlling a fluid flow to and/or from the hydraulic actuator.