Parts for your 2015 Subaru Exiga-Thermostat housing

2015 Subaru Exiga Thermostat Housing

Referencing Subaru’s official service information (STIS Workshop Manual: Exiga YA-series Cooling System, 2014–2015) and the Subaru FAST electronic parts catalogue for the YA Exiga, the 2015 Subaru Exiga is fitted with a thermostat and a thermostat housing (often called the thermostat cover or water inlet) mounted at the water pump on the lower radiator hose side. So a thermostat housing is absolutely relevant on this model.

On the 2015 Exiga’s flat-four (EJ/FB family), the thermostat housing does a simple but crucial job: it holds the thermostat, seals the coolant passage, and forms the outlet/inlet to the lower radiator hose. As the engine warms, the thermostat opens at its rated temperature, letting coolant circulate through the radiator. The housing keeps that flow controlled and leak-free, helping the boxer engine reach operating temp quickly and then stay there, which keeps fuel economy tidy and the heater working properly on a frosty morning.

During regular servicing, it’s smart to give the thermostat housing some attention whenever the coolant is changed or the water pump is off. Check for seepage around the housing joint, condition of the O-ring/gasket, and any warping or corrosion on alloy housings, or cracking on plastic types. If the thermostat is being replaced, renew the housing seal as well—cheap insurance against annoying leaks.

Many workshops will replace the thermostat and housing seal at the same time as a timing belt and water pump on EJ-equipped variants, or opportunistically during major cooling-system work. While there’s no strict kilometre-based replacement for the housing itself, symptoms that call for immediate inspection include:

• Coolant leaks at the lower radiator hose outlet or housing joint
• Erratic temperature gauge behaviour, slow warm-up, or overheating
• Dried coolant crust around the housing or a sweet smell under the bonnet

When refitting, use the correct gasket/O-ring orientation, clean mating surfaces, and torque the housing bolts to factory spec from the Subaru manual. Top up with the Subaru-specified long-life coolant and bleed air carefully—Subaru boxers are a bit particular about proper bleeding. Done right, the Exiga’s thermostat housing will get on with its job quietly for years, keeping school runs, weekend trips, and long Kiwi or Aussie highway stints drama-free.

Popular questions about the 2015 Subaru Exiga thermostat housing

Where is the thermostat housing located on a 2015 Exiga?
It sits at the front of the engine on the lower side, integrated with the water pump area, where the lower radiator hose connects. Access is from the front under the bonnet, on some variants, removing the undertray or intake ducting makes life easier.

Do I need to replace the housing when changing the thermostat?
Not always. If the housing isn’t cracked, warped, or corroded, it can be reused. Always fit a new O‑ring or gasket, and inspect the sealing surface. If there’s any doubt—or you’re already in there for a water pump—replacing the housing is a sensible, low-cost preventive step.

What coolant should be used after housing or thermostat work?
Use Subaru-approved long-life coolant (often the blue “Super Coolant”) mixed to the correct ratio. Proper bleeding is essential to avoid air pockets that can cause hot spots or erratic temps.