Where does the o-ring go on my sport trac thermostat?

The O-ring on your Ford Sport Trac's thermostat is typically placed in the groove of the thermostat housing. It creates a seal between the thermostat and the housing, preventing coolant leaks. Ensure that the O-ring is properly seated before reassembling to ensure a tight fit. Always refer to your vehicle's service manual for specific instructions related to your model.