Parts for your 2013 Subaru Legacy-Thermostat housing

Thermostat Housing for the 2013 Subaru Legacy (BR/BM)

Yes, the 2013 Subaru Legacy does use a thermostat housing. Subaru technical sources identify it as the “water inlet” or “thermostat cover,” bolted to the water pump at the lower radiator hose. This setup is documented in the Subaru Legacy/Outback BR/BM Service Manual (Cooling System section) and reflected in Subaru’s parts catalogue for both FB25 2.5L and EZ36 3.6L engines. In plain terms: the thermostat sits in a dedicated housing at the pump inlet, sealing with an O-ring and providing the hose connection that feeds coolant into the engine.

On the 2013 Legacy, the thermostat housing’s job is to hold and seal the thermostat, direct coolant flow into the engine, and give a solid mounting for the lower radiator hose. When the engine’s cold, the thermostat stays shut to help it warm up quickly, as it reaches operating temp, the thermostat opens, allowing coolant from the radiator to circulate. The housing must stay true and leak-free so the thermostat can do its thing without drama.

As part of regular servicing, it’s worth eyeballing the housing and hose area under the bonnet for any white crust, damp tracks, or staining. The factory plastic/metal housing can harden or warp with age and heat cycles, especially past the 10-year mark. If the thermostat’s being replaced, it’s smart to fit a fresh O-ring and inspect the housing’s sealing face. Many techs choose to renew the housing if it’s brittle, pitted, or the hose nipple looks tired.

• Common clues it’s time: coolant seepage at the housing, overheating, slow warm-up, temp gauge wandering, or radiator fans running excessively.
• Always use the correct Subaru-spec long-life coolant (don’t mix colours) and a quality thermostat/O-ring.

1. Let the engine cool, then drain enough coolant to drop the level below the housing.
2. Remove the lower hose, unbolt the housing, and lift out the thermostat.
3. Clean mating surfaces, fit the new thermostat with the jiggle pin/air bleed at the top, and install a new O-ring.
4. Refit the housing to the specified torque (per Subaru manual), reconnect the hose and clamps.
5. Refill with the correct coolant, bleed air with the heater on hot, and check for leaks and stable temps.

Handled properly, it’s a straightforward job that keeps the Legacy running at the right temperature and sipping fuel as it should.

Where is the thermostat housing on a 2013 Subaru Legacy?

It’s at the front lower side of the engine, where the lower radiator hose meets the water pump. Subaru calls this piece the water inlet/thermostat cover, and the thermostat sits behind it sealed by an O-ring.

Should the housing be replaced with the thermostat?

Not always. If the housing is flat, crack-free, and the hose nipple is sound, a new O-ring and thermostat will do. Replace the housing if it’s warped, brittle, or shows persistent leaks after reassembly.

What coolant should be used after replacing the thermostat/housing?

Use Subaru-spec long-life coolant (often the blue formulation) or an equivalent that meets Subaru requirements. Avoid mixing types, stick with the same chemistry and flush if switching.