Yamaha Thermostat Seal 67F-12412-00-00. Overview. The Yamaha Thermostat Seal 67F-12412-00-00 is a genuine original equipment manufacturer component designed to create a secure seal around the thermostat within the engine cooling system. This seal helps prevent coolant leaks and ensures the thermostat housing maintains proper pressure and water flow during engine operation.. A properly functioning thermostat seal is essential for maintaining cooling system efficiency. Over time, seals can become