Parts for your 2016 Subaru Impreza-Thermostat

2016 Subaru Impreza Thermostat — What It Does and When to Replace It

Yes, the 2016 Subaru Impreza uses a thermostat. Technical references including the Subaru Workshop Manual for GP/GJ (MY2016) Cooling section and Subaru’s Electronic Parts Catalogue list a wax‑pellet engine coolant thermostat fitted to the FB20 boxer engine. It’s mounted at the engine water inlet where the lower radiator hose meets the front of the engine, so it’s absolutely relevant to cooling performance on this model.

The thermostat’s job is to help the engine warm up quickly and then keep it at a stable operating temperature. When the engine’s cold it stays shut, circulating coolant only through the block to bring temps up quickly for better fuel economy, lower emissions, and a toasty heater under the bonnet. As the coolant reaches the factory‑set temperature, the thermostat opens and meters flow through the radiator, teaming up with the fans and ECU strategy to keep things rock steady whether it’s peak‑hour traffic or an alpine run.

On a 2016 Impreza, the thermostat isn’t a routine “every X kilometres” replacement item, but it should be inspected during coolant services. Telltale signs it’s on the way out include slow warm‑up, fluctuating or creeping temperature gauge, poor cabin heat, overheating at highway speed, or a check engine light with a code like P0128 (coolant below regulating temperature). Any overheat event is also a good reason to consider a fresh thermostat.

When replacement is due, stick with a genuine‑spec thermostat and a new O‑ring/seal. Fitment lives at the water inlet under the front of the engine, clean the mating surfaces carefully and orient any bleed jiggle‑pin as per the workshop manual. Refill with the correct Subaru long‑life coolant, bleed air thoroughly (nose slightly uphill helps), set the heater to HOT, and run the engine until the fans cycle a couple of times. Top up the reservoir once it cools and check for leaks. Dispose of old coolant responsibly—it’s toxic to pets and wildlife.

While the job is straightforward with basic tools, always follow factory torque specs and safety steps. Regular coolant changes per the service logbook and a healthy radiator cap will help the thermostat do its best work for years.

• Common symptoms: slow warm‑up, temp gauge wandering, weak heater, overheating at speed, code P0128.
• Best practice: use OEM‑quality parts, new O‑ring, correct coolant, and thorough bleeding.

FAQs

Where is the thermostat on a 2016 Subaru Impreza?
It’s located at the engine water inlet where the lower radiator hose connects to the front of the FB20 engine, behind a small aluminium housing near the oil filter area. Access is from under the front of the car or from above with the intake ducting moved, depending on tools and setup.

Do I need to replace the thermostat every time I change the coolant?
No. It’s not a scheduled item and can last many years. Replace it if there are symptoms of sticking, after an overheating incident, or if inspection shows corrosion or a damaged seal. If you remove it during other work, fit a new O‑ring.

Is it safe to drive with a P0128 code on this Impreza?
Usually the car remains drivable, but the engine may run too cool, causing higher fuel use and poorer heater performance. It’s best to book in diagnosis and likely thermostat replacement soon to protect the engine and maintain efficiency.