Parts for your 2016 Subaru Impreza-Thermostat housing

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

Yes, the 2016 Subaru Impreza uses a thermostat housing. Technical references including the Subaru Service Manual for the FB20 engine (Cooling section), Subaru FAST parts catalogue diagrams (showing the “water inlet/thermostat cover”), and independent workshop manuals for 2012–2016 Impreza models all confirm that the thermostat is mounted in a housing at the water pump inlet. That assembly is commonly called the thermostat housing or water inlet.

On the 2016 Impreza, the thermostat housing’s job is simple but critical: it holds the thermostat, seals the coolant path with an O‑ring, and directs coolant from the lower radiator hose into the water pump. By opening and closing with temperature, the thermostat helps the engine warm up quickly and then keeps it in the sweet spot for performance and longevity. The housing provides a stable, leak‑free mount so the system can maintain correct pressure and flow.

As part of routine servicing, it pays to give the housing and surrounding hoses a quick once‑over. Look for crusty white or pink residue, dampness around the housing seam, or perishing at the hose neck. On higher‑kilometre cars, plastic/composite inlets can warp or crack from age and heat cycling. If there’s any doubt, replacement is straightforward and often wise to do at the same time as a thermostat or coolant service.

• Common clues it needs attention: slow warm‑up, temp gauge fluctuations, poor cabin heat, overheating at speed, or visible coolant seepage near the lower radiator hose.
• Coolant choice and intervals matter: run a Subaru‑approved long‑life blue coolant and refresh it per the maintenance schedule, shorter intervals apply if using non‑OEM green coolant.

1. Let the engine cool fully, then drain enough coolant to drop the level below the housing.
2. Remove the lower radiator hose and the housing bolts, expect some spillage.
3. Inspect and clean mating surfaces. Fit a new thermostat and O‑ring, matching the orientation (jiggle valve at 12 o’clock if specified by the service manual).
4. Reinstall the housing, tightening bolts to the service‑manual torque, and refit the hose with a sound clamp.
5. Refill with the correct premix, bleed air with the heater on hot, and let the fans cycle. Top up the overflow and recheck for leaks after a short drive and again next morning.

Handled this way, the thermostat housing will stay leak‑free and the Impreza’s FB20 will run right on temperature, day in and day out.

Popular questions about the 2016 Subaru Impreza thermostat housing

Where is the thermostat housing on a 2016 Impreza?
It’s at the front lower side of the engine, bolted to the water pump. The lower radiator hose connects directly to it. Access is usually easiest from underneath after removing the under‑tray.

How often should the thermostat or housing be replaced?
There isn’t a fixed interval. Replace the thermostat and housing when there are symptoms (overheating, slow warm‑up, leaks) or when you’re already doing major cooling‑system work. Always use a new O‑ring and quality parts to avoid repeat leaks.

Do I need to bleed the system after replacing the housing?
Yes. Air pockets can cause hot spots and erratic temperature readings. Refill with the correct Subaru‑approved long‑life blue coolant, run the heater on full hot, and bleed until bubbles stop and the cooling fans cycle normally. Recheck the level after a short drive.