Parts for your 2014 Subaru Impreza-Thermostat

2014 Subaru Impreza Thermostat — What it does and how to look after it

Yes, the 2014 Subaru Impreza absolutely uses a thermostat. Technical sources confirm it: the Subaru Service Manual for the 2012–2016 GP/GJ Impreza (FB20 engine) lists a wax‑pellet thermostat in the cooling system, mounted at the water inlet housing on the lower radiator hose side. Subaru’s OEM parts catalogue also shows this component for the FB20 (e.g., thermostat p/n 21200AA072 with matching seal). So it’s very much a relevant, fitted part on this model.

On this Impreza, the thermostat’s job is to help the engine warm up quickly and then hold a steady operating temperature. It stays closed when the engine’s cold to speed up warm‑up, then opens around the specified temperature to let coolant circulate through the radiator. The result is stable engine temps, better fuel economy, consistent heater performance under the bonnet and in the cabin, and reduced wear on cold starts.

There’s no strict replacement interval in the maintenance schedule, so it’s usually changed when there are symptoms or during larger cooling system work. Many owners opt to replace it during a coolant service, or if chasing temperature issues. Using a genuine or high‑quality thermostat and a fresh gasket/O‑ring is key, and sticking with the correct temperature rating for the FB20 is a must.

• Common signs it’s on the way out: slow warm‑up or the gauge dropping on long downhill runs, overheating under load, temp gauge hunting, heater going cold/hot, or a Check Engine Light with code P0128 (coolant temp below thermostat regulating temp).

Handy service pointers for the Impreza:

1. Work only on a stone‑cold engine and catch old coolant cleanly.
2. The thermostat sits in the water inlet at the lower radiator hose—note its orientation when removing.
3. Fit the new unit with a new seal, clean the mating surfaces, and tighten the housing evenly with a small spanner—no need to swing off it.
4. Refill with the correct Subaru‑spec long‑life coolant mix, bleed air using the header tank, and run the heater on full hot while topping up.
5. Check for leaks and recheck the level after a decent drive. Dispose of old coolant responsibly.

Look after the cooling system—hoses, clamps, radiator, cap, and thermostat—and the FB20 will rack up the kays without a fuss.

FAQs

What temperature rating thermostat does a 2014 Impreza use?
Typically it’s in the high‑80s to around 90°C opening range for the FB20. The exact spec can vary by market and VIN, so matching an OEM‑equivalent thermostat to the vehicle’s details is the safest bet.

Does the thermostat need regular replacement?
There’s no fixed interval. Replace it if there are symptoms, a fault code like P0128, contamination from previous overheating, or as smart preventative maintenance during a major coolant service.

Where is the thermostat located on the 2014 Impreza?
It lives in the water inlet housing where the lower radiator hose meets the front of the engine. Two bolts, a seal, and it comes out—just make sure the engine’s cold and the coolant is drained to avoid a mess.