Parts for your 2016 Subaru Outback-Thermostat

2016 Subaru Outback thermostat — what it does and how to look after it

A thermostat is absolutely fitted to the 2016 Subaru Outback. Technical references including the Subaru Service Manual for 2015–2019 Outback/Legacy (Cooling System section), Subaru genuine parts catalogues for FB25 (2.5i) and EZ36 (3.6R) engines, and common aftermarket catalogues (Gates, Stant, Mahle) all list a dedicated engine coolant thermostat for this model, positioned at the water pump inlet via the lower radiator hose. So it’s not an optional extra — it’s a core part of the cooling system.

In day-to-day driving, the thermostat controls coolant flow so the engine warms up quickly, then stays near its designed operating temperature. That sweet spot helps with fuel economy, emissions, engine longevity, and cabin heater performance. If it sticks shut, the Outback can overheat, if it sticks open, it’ll take ages to warm up, run rich, and the heater will be lukewarm — often flagged by a P0128 fault code.

For servicing, the thermostat isn’t a routine “every X kilometres” replacement item on this Outback — Subaru’s guidance is to inspect and replace if there are symptoms or if the cooling system is being overhauled. Many owners choose to fit a new genuine thermostat when doing a major coolant service or water pump job. Always use the correct coolant (Subaru Super Coolant/“blue” long-life, or a compatible equivalent) and never mix types.

Handy signs it’s time to check or replace the thermostat:

• Temp gauge wandering, slow warm-up, or sudden spikes
• P0128 stored, poor heater output, or high idle longer than normal
• Overheating under load with the radiator fan working hard

Replacement tips for a 2016 Outback:

• Location: at the lower radiator hose housing on the front of the engine, integrated with the water pump inlet, access is easiest from underneath after removing the undertray.
• Drain enough coolant to drop the level below the housing. Fit a new O-ring/gasket, clean the mating surfaces, and tighten bolts to spec — don’t overdo it.
• Refill with the correct coolant mix, bleed air thoroughly (heater on full hot), and check for leaks. Top up the reservoir after a couple of heat cycles.

Look after the cooling system — good coolant, clean radiator fins, healthy cap and hoses — and the thermostat in a 2016 Outback will usually give long, drama-free service.

Popular questions

Where is the thermostat on a 2016 Subaru Outback?
It lives at the lower radiator hose connection on the front of the engine, built into the water pump inlet housing. On both the 2.5i (FB25) and 3.6R (EZ36), access is typically from underneath once the splash shield is off.

Does the thermostat need regular replacement?
Not on a fixed schedule. Replace it if there are symptoms (overheating, slow warm-up, temp fluctuations, P0128) or when doing major cooling system work. Always use the correct long-life coolant and bleed the system properly.

What coolant should be used after thermostat work?
Use Subaru’s long-life “blue” Super Coolant or a fully compatible equivalent meeting the same spec. Don’t mix coolant types. After refilling, bleed air with the heater on hot and recheck the level over the next few drives.