Could the thermostat be in lower radiator hose?

Yes, in some engines, the thermostat housing may be located on the lower radiator hose. This type of thermostat is known as a lower hose thermostat. It functions by regulating the flow of coolant between the engine and the radiator. When the engine is cold, the thermostat remains closed, preventing coolant from flowing to the radiator. This allows the engine to reach its optimal operating temperature quickly. Once the engine reaches a predetermined temperature, the thermostat opens, allowing the coolant to flow through the radiator, thus cooling the engine down.