Mercury 3L3Z-8575-AC Thermostat Assembly

Don't drive without a thermostat as it can affect emissions and fuel economy. Before blaming the thermostat, check coolant level, drivebelt tension, and temperature gauge. If the engine takes long to warm up or runs hot without the upper radiator hose being hot, the thermostat is likely faulty and needs replacement. Overheating can cause engine damage. To replace the thermostat, drain coolant below the thermostat housing level, disconnect the upper radiator hose, remove the cover and O-ring seal, and note the thermostat's installation. Install a new thermostat with the correct opening temperature, clean the mating surfaces, and apply RTV sealant to a new gasket or O-ring seal. Reattach the cover, radiator hose, refill the system, check for leaks, and repeat steps if necessary.