Parts for your 2012 Subaru Forester-Thermostat

2012 Subaru Forester thermostat — what it does and when to replace it

Yes, a thermostat is fitted to the 2012 Subaru Forester. Subaru factory service information and OEM parts catalogues for the 2012 Forester (FB-series 2.5 petrol and market variants of EJ25) specify a wax‑pellet engine thermostat located at the water pump outlet in the lower radiator hose area. Its calibrated opening temperature is typically around 78–82°C, ensuring the engine warms promptly and then holds a steady operating temperature.

The thermostat’s job is simple but crucial. When the engine’s cold, it stays shut so coolant doesn’t circulate through the radiator, helping the Forester warm up quickly for better fuel economy, lower emissions, and good cabin heat. Once it reaches temp, the thermostat opens to regulate coolant flow through the radiator, keeping things stable under load, on long climbs, or slogging through city traffic.

They do age. A thermostat stuck open can cause slow warm‑up, poor heater performance, lumpy fuel economy and the classic P0128 code. Stuck closed can mean rapid overheating, hard hoses, and the temp gauge spiking. Either way, it’s worth sorting promptly to protect the engine.

• Good times to replace: during a major coolant service, when doing a water pump, after an overheating event, or if there’s any sign of sticking.
• What to use: a quality, correct‑spec thermostat and a new O‑ring/seal. On Subarus, orientation matters—fit it with the jiggle pin/air bleed as specified.

Service pointers for a 2012 Forester thermostat swap under the bonnet:

1. Work stone‑cold. Drain the coolant cleanly.
2. Access the lower radiator hose/housing at the water pump, clean mating surfaces, and install the new thermostat and seal carefully.
3. Torque housing bolts evenly and modestly (don’t overdo it).
4. Refill with Subaru‑approved premix coolant. Bleed air—nose‑up helps—heater on full hot, run to operating temp, top up and fit the cap.

Preventative care makes life easy: keep coolant fresh per Subaru’s schedule, check the radiator cap and hoses, and watch the temp gauge on long motorway runs. Many owners sensibly pair thermostat replacement with coolant service intervals so everything stays ship‑shape for the next 100,000 km or so. After replacement, confirm steady temps, strong cabin heat, and no leaks—then enjoy the drive.

Where is the thermostat on a 2012 Subaru Forester?

It’s fitted at the water pump outlet in the lower radiator hose area, front of the engine. Access is usually from underneath after draining the coolant, removing the lower hose and the small housing that retains the thermostat.

What temperature does the Forester’s thermostat open?

Most 2012 Forester units begin opening around 78–82°C and are fully open roughly in the low‑to‑mid 90s°C. Always match the replacement to the Subaru‑specified rating stamped on the thermostat.

Should it be changed during routine servicing?

It doesn’t need changing every service, but it’s smart to replace it during a major coolant service, with a water pump change, or if there are symptoms like slow warm‑up, P0128, fluctuating temps or overheating. Using a fresh seal and properly bleeding the system are key.