Order Subaru Impreza Bypass Valve Cooling System. Find Subaru Impreza Thermostats. Get Subaru Impreza Thermostat Gauge & Subaru Impreza Coolant Thermostat Price. Maintaining the thermostat in your Subaru Impreza is crucial for regulating the engine's temperature and ensuring optimal performance. Signs that may indicate the need for replacement include fluctuating temperatures, overheating, and poor cabin heating. To extend the lifespan of your thermostat, ensure regular cooling system flushes and use manufacturer-recommended coolant. When choosing a replacement, consider OEM thermostats for guaranteed compatibility or aftermarket options that offer unique features such as fail-safe designs. Always prioritize high-quality materials for durability, and for DIY enthusiasts, remember to adhere to installation guidelines to avoid damage to your vehicle's engine.