Parts for your 2022 Subaru Impreza-Thermostat

2022 Subaru Impreza thermostat — purpose, servicing and when to replace

Technical sources confirm the 2022 Subaru Impreza is fitted with a conventional engine coolant thermostat. Subaru factory service information (STIS) for the GK/GT Impreza (FB20 engine) describes a wax‑pellet thermostat installed in the water inlet housing at the lower radiator hose/water pump side. Subaru genuine parts catalogues list a dedicated thermostat and seal for the 2.0‑litre FB engine, and major application guides from Gates and Dayco also specify direct‑fit replacements. So, yes — the thermostat is definitely used on the 2022 Impreza and it plays a critical role in temperature control.

The thermostat’s job is to help the engine warm up promptly, then hold it at the sweet‑spot temperature for efficiency, performance and emissions. When the coolant is cold, the valve stays shut to speed warm‑up under the bonnet, as temperature rises, it opens progressively to route coolant through the radiator. The result is steadier gauge readings, better heater performance on a cold morning, and reduced wear and fuel use.

As part of routine servicing, the thermostat doesn’t usually need attention at every coolant change, but it should be evaluated any time there are cooling concerns or when the water pump is being replaced. Common clues a thermostat’s on the way out include:

• Overheating at speed or in traffic, or the opposite — very slow warm‑up and a heater that stays lukewarm.
• Temp gauge wandering or sudden spikes, engine code P0128 (coolant temp below regulating range).
• Radiator hoses showing big temperature differences after a decent drive.

If replacement is needed on a 2022 Impreza, standard practice is:

1. Allow the engine to cool fully and safely relieve system pressure.
2. Drain enough coolant to sit below the housing, then remove the lower hose/water inlet housing.
3. Swap the thermostat and seal, matching the orientation (air‑bleed jiggle pin, if fitted, typically up).
4. Reassemble, torque the housing bolts evenly, and refill with Subaru‑approved long‑life blue coolant (premix).
5. Bleed air from the system, run the engine with the heater on, and top up once cooled.

For Aussie and NZ conditions, many workshops inspect the thermostat at each major cooling‑system service (often around 100,000–150,000 km), or replace it proactively when chasing intermittent temp swings. Sticking to correct coolant, good caps and clean radiators will help the Impreza’s thermostat live a long, drama‑free life.

FAQs

Where is the thermostat on a 2022 Subaru Impreza?
The thermostat sits in the water inlet housing on the lower radiator hose side of the engine, at the front of the FB20 near the water pump. Access is typically from underneath once the under‑tray is removed and coolant is lowered below the housing level.

What are the signs the Impreza’s thermostat needs replacing?
Tell‑tales include slow warm‑up, a heater that won’t get properly hot, erratic temperature readings, overheating under load, or a P0128 fault. If the top hose stays cold long after start‑up, or temperature spikes then suddenly drops, the valve may be sticking.

Should the thermostat be replaced during routine coolant changes?
Not automatically. If the existing thermostat tests fine and there are no symptoms, it can stay. Many technicians do replace it preventatively when doing a water pump, chasing temp instability, or at higher kilometres to avoid repeat labour later.