Calorstat TH6736.78J Engine Coolant Thermostat

Engine Coolant Thermostat for Subaru Applications

Calorstat TH6736.78J is an engine coolant thermostat built for Subaru cooling system service, with fitment across multiple Legacy, Outback, Impreza, Forester, Baja, WRX, and WRX STI applications. It opens at 172°F (78°C) and includes a gasket seal for a direct replacement installation.

Key Features

• Engine coolant thermostat with standard design
• Opening temperature: 172°F / 78°C
• Off-set valve seat design for the specified application
• Gasket included with rubber seal material
• Sealing flange outside diameter: 2.2
• Height between flanges: 1.33
• Cross-references to select Carlson, Four Seasons, Gates, and Motorad part numbers

Detailed Description

Calorstat TH6736.78J is a standard engine coolant thermostat engineered for Subaru cooling system control. By regulating coolant flow at the specified 172°F opening temperature, it helps maintain proper engine operating temperature in Subaru Legacy, Outback, Impreza, Forester, Baja, WRX, and WRX STI models. The included gasket seal supports a clean replacement at the thermostat housing interface, and the off-set valve seat design matches the listed application requirements. This part number, TH6736.78J, is a direct-fit service option for a wide range of Subaru cooling repairs.

This part cross-references Carlson 14147 and Gates 33857 for the same application.

What It Helps Address

• Engine running too cool or too warm due to thermostat wear
• Delayed coolant circulation during warm-up
• Temperature fluctuation caused by a sticking thermostat
• Cooling system service on Subaru Legacy, Outback, Impreza, Forester, Baja, WRX, and WRX STI models
• Thermostat housing reseal service when replacing the thermostat

Installation Notes and Tips

• Verify the thermostat opening temperature matches the vehicle specification before installation.
• Inspect the thermostat housing and sealing surfaces for corrosion, pitting, or debris.
• Use the included gasket seal during installation and ensure proper seating.
• Refill and bleed the cooling system according to Subaru service procedures after replacement.
• Confirm fitment by year and model, especially on 2007-2009 Outback applications with date-specific coverage.

Quality Assurance

Calorstat TH6736.78J is built as a standard replacement thermostat for the listed Subaru applications and is specified with defined dimensions, seal type, and opening temperature for accurate cooling system service.

• Fits 2013-2020 Subaru WRX STI, N/A
• Fits 2015-2019 Subaru Legacy, N/A
• Fits 1995-2009 Subaru Legacy, N/A
• Fits 2015-2019 Subaru Outback, N/A
• Fits 2000-2006 Subaru Outback, N/A
• Fits 1995-2014 Subaru Impreza, N/A
• Fits 2013-2014 Subaru WRX, N/A
• Fits 1998-2013 Subaru Forester, N/A
• Fits 2009 Subaru Outback, N/A
• Fits 2008 Subaru Outback, N/A
• Fits 2007 Subaru Outback, N/A
• Fits 2003-2006 Subaru Baja, N/A