If your Subaru takes really a long time to come up to operating temperature, or maybe it just runs hot all the time, there’s a good chance it’s a stuck coolant thermostat for the radiator. Don’t bother replacing it with a parts-store generic ‘stat, because they may not have the right hole size for proper flow. Use the factory part. You’ll thank us later.
Gasket sold separately.
Fits all 2002+ EJ motor Subaru cars, including 2002-2014 Subaru WRX and 2004-2021 WRX STI.