Motorad Fail-Safe Thermostats offer premium, patented technology for superior protection over any thermostat on the market. Only Fail-Safe is designed to lock in the open position when overheating occurs due to a failing cooling system component. This allows maximum coolant flow, thus preventing expensive engine damage. When standard thermostats fail, they lock in the closed position and prevent coolant flow to the engine. Fail-Safe has a patented safeguard against overheating damage.