Parts for your 2013 Subaru Forester-Thermostat housing

2013 Subaru Forester Thermostat Housing: What It Does and When To Replace It

Yes, a thermostat housing is absolutely used on the 2013 Subaru Forester. Subaru’s factory service manual for the 2013 Forester cooling system, along with the Subaru Genuine Parts Catalogue for the FB25 (2.5i) and EJ255 (XT) engines, shows a bolt-on thermostat housing (also called a thermostat cover/outlet) mounted at the water pump inlet where the lower radiator hose connects. These technical sources confirm the part is relevant to this model year and engine range.

On the 2013 Forester, the thermostat housing does more than simply “hold” the thermostat. It seals the thermostat to the water pump, directs coolant from the lower radiator hose, and helps manage bypass flow while the engine warms up. That means stable operating temperature, better heater performance, and consistent fuel economy. If the housing or its O-ring leaks, it can cause coolant loss, overheating, or annoying drips on the driveway.

Owners looking after their Forester should treat the housing and thermostat as part of routine cooling-system care. During coolant changes, it’s smart to inspect around the lower hose connection at the front of the engine for any white crust, staining, or dampness. Anytime the thermostat is removed, a fresh genuine O-ring or gasket should be fitted, the mating surfaces cleaned without gouging, and the bolts tightened evenly to the factory specification—no over‑torquing. Subaru-approved long‑life blue coolant should be used, and the system bled properly so no air pockets hang about.

Typical signs the housing or seal needs attention include:

• Coolant smell and small drips under the front of the engine after parking
• Temperature gauge wandering or slow warm‑up (if the thermostat itself is sticking)
• Visible seepage around the housing flange or lower radiator hose neck

When replacing the thermostat, many techs prefer genuine parts for correct opening temperature and the proper bleed feature. The thermostat orientation matters—follow the workshop manual so the bleed pin or mark is positioned correctly. Avoid using RTV on the O‑ring groove, it should seal cleanly when parts are true. After reassembly, refill, bleed with the heater on hot, and pressure test to confirm it’s watertight. If the housing is pitted, warped, or cracked, replacing it along with the thermostat saves time and reduces the risk of repeat leaks. Look after this small bit of kit and the Forester’s cooling system will stay happy for plenty of kilometres.

Popular questions about the 2013 Subaru Forester thermostat housing

Where is the thermostat housing located?
It’s mounted at the water pump inlet on the lower front of the engine, right where the lower radiator hose connects. On both FB25 and EJ255 engines used in 2013, you’ll reach it from underneath or the front once the splash shield is off.

Do I need to replace the housing when changing the thermostat?
Not always. If the housing sealing face is clean and flat and the neck isn’t corroded or cracked, it can usually be reused with a new genuine O‑ring. Replace the housing if there’s pitting, warping, or damage that could cause leaks.

What coolant should be used and do I need to bleed the system?
Use Subaru‑approved long‑life blue coolant (the correct spec for this model). Yes—bleeding is important. Fill slowly, run the heater on hot, and burp the system so trapped air doesn’t cause hot spots or temp gauge swings.