Parts for your 2023 Subaru Impreza-Thermostat

2023 Subaru Impreza Thermostat – Purpose, Care and When to Replace

The 2023 Subaru Impreza does use a thermostat. Subaru’s factory service literature for the FB-series 2.0L engine fitted to the 2023 model specifies a wax‑type thermostat (opening temperature around 88°C) located at the water pump inlet on the lower radiator hose side. The official Subaru parts catalogue likewise lists a dedicated thermostat assembly and gasket for this vehicle. So the thermostat is absolutely relevant to the 2023 Impreza’s cooling system.

In plain terms, the thermostat helps the engine warm up quickly and then keeps it sitting in the sweet spot for temperature. When the engine is cold it stays shut, speeding warm‑up for better fuel economy and smoother running. Once coolant reaches its set temperature, it opens and lets coolant circulate through the radiator to prevent overheating. That consistent temperature is key to engine longevity, steady heater performance and stable emissions.

For servicing, the thermostat isn’t a scheduled replacement item on its own, but it should be inspected any time there are cooling‑system concerns or when major work is being done. Many workshops will replace it preventatively when fitting a new water pump, after a significant overheating event, or if fault code P0128 (coolant temperature below thermostat regulating temperature) pops up. Always use a genuine‑quality thermostat and a new gasket or seal, and refill with the correct Subaru long‑life coolant. Bleeding the system properly is crucial on the FB engine to avoid air pockets.

• Common clues it’s on the way out: slow warm‑up or the temp gauge sitting low on the motorway, weak cabin heat, fluctuating temperature, overheating in traffic, cooling fans running excessively, or coolant staining around the housing.
• Basic care: keep to the coolant change intervals in the maintenance schedule, check hoses and clamps for condition, and investigate any small leaks before they become big problems. Always work on the cooling system only when the engine is stone cold.

For DIY replacement, the thermostat housing is at the bottom front of the engine near the lower radiator hose. Expect some coolant loss