Parts for your 2009 Subaru Exiga-Thermostat housing

2009 Subaru Exiga Thermostat Housing

Based on the Subaru Factory Service Manual for the EJ-series engines used in the 2009 Subaru Exiga (YA chassis) and Subaru’s FAST electronic parts catalogue, the vehicle does use a thermostat housing. Subaru often labels this piece as the “water inlet” or “thermostat cover.” It bolts to the front of the water pump and carries the lower radiator hose while clamping the thermostat in place—so it’s very much a relevant, fitted component on the 2009 Exiga.

The thermostat housing’s job is straightforward but critical. It locates the thermostat precisely, seals the coolant pathway with an O-ring, and directs coolant between the radiator and the engine. Because it forms the interface for the lower radiator hose, it also cops the brunt of heat cycling and hose clamp pressure. On the EJ20 engines found in the Exiga, that housing helps maintain stable operating temperature, good cabin heat, and consistent fuel economy.

As part of servicing, most techs treat the housing whenever the thermostat is replaced. Even if the housing itself isn’t worn out, the sealing O-ring should always be renewed. If the housing shows corrosion, pitting around the seal land, warped mating faces, or a hairline crack near the hose neck, it’s time to fit a new one. Follow the Subaru FSM for torque specs on the housing bolts—overtightening can distort the alloy and cause leaks.

Use a quality thermostat that suits the EJ engine and sit the jiggle pin at 12 o’clock to help purge air. Lightly lubricate the new O-ring with fresh coolant, clean the pump’s mating surface, and ensure the hose clamp sits behind the bead on the neck. Refill with the correct Subaru-approved long-life coolant mix, run the heater on full hot, and bleed the system thoroughly to avoid airlocks that can trigger overheating or weak cabin heat.

Common signs the thermostat housing or seal needs attention include fresh coolant tracks around the lower hose area, sweet coolant smells after a drive, slow warm-up or fluctuating temps, and drops in the overflow bottle.

• Recommended practice: replace the housing when it’s damaged or corroded, and always replace the O-ring with the thermostat.
• Stick with genuine or high-quality aftermarket parts that match the Exiga’s EJ engine spec.

FAQs

Where is the thermostat housing on a 2009 Subaru Exiga?
On EJ-powered Exigas, it’s the alloy “water inlet” bolted to the front of the water pump, facing forward at the bottom of the engine. The lower radiator hose connects directly to it.

Should the housing be replaced with the thermostat?
Not always, but it’s wise to inspect it closely. Replace the housing if it’s corroded, pitted, cracked, or warped. The O-ring seal should always be renewed with the thermostat.

What coolant should be used after replacing the housing?
Use a Subaru-approved long-life coolant suitable for aluminium engines and mix to the manufacturer’s spec. Bleed the system carefully to remove air.