Thermo Valve (Federal Models)

Thermo valve is used to sense engine coolant temperature and prevent EGR operation when below preset value. When engine warms up, thermo valve opens to allow vacuum passage to EGR valve, which then determines EGR flow. Below 113°F (45°C), thermo valve is open, causing vacuum to be vented, thus not reaching EGR valve. Above 131 °F (55°C), thermo valve closes and normal EGR operation is accomplished.