Fail-Safe is designed to help protect your engine when overheating occurs. When overheating occurs, Fail-Safe automatically locks in the open position to permit maximum coolant flow. When standard thermostats fail, they lock in the closed position and prevent coolant flow to the engine, which can possibly cause serious damage to your engine. Fail-Safe has a patented safeguard against overheating damage. Fail-Safe thermostats are designed with a unique extra stroke that allows operation in two stages. Within normal operating temperatures, the Fail-Safe operates the same as any other thermostat. When overheating is caused by a deteriorating cooling system part, the Fail-Safe has a secondary stroke that activates a precision engineered piston that automatically locks the valve into a wide open position allowing coolant to circulate freely.