THERMO Valve

The thermo valve, which is located adjacent to the thermostat, prevents vacuum to the upper diaphragm of the EGR valve when the coolant temperature is below 113°F (45°C). This lack of vacuum results in upper diaphragm being closed by the return spring, thereby preventing any exhaust gas recirculation when the engine is cold. When the thermo valve is open and supplying vacuum, the lower diaphragm of EGR valve then controls normal EGR flow.