Parts for your 2009 Nissan Serena-Thermostat housing

2009 Nissan Serena thermostat housing — what it does and how to look after it

Technical documentation confirms the 2009 Nissan Serena does use a thermostat housing. The C25-series Serena (typically with the MR20DE 2.0‑litre engine) is shown in the Nissan C25 Serena Service Manual — Cooling System (CO) section with a separate thermostat and “water inlet”/housing. The Nissan Electronic Parts Catalogue (FAST/EPC) also lists a dedicated water inlet/thermostat housing for MR20DE applications used in the 2009 Serena (commonly referenced under Nissan part group 11060 for the housing and 21200 for the thermostat). These sources verify the housing is a relevant and fitted component on this model.

On the 2009 Serena, the thermostat housing does more than hold the thermostat, it forms the main junction where coolant leaves or enters the engine, ties in the lower radiator hose, and provides a sealed seat for the thermostat and its O‑ring. It helps the cooling system reach operating temperature quickly, then maintains it so the Serena runs efficiently, gives reliable cabin heat, and avoids overheating.

As part of routine servicing, it’s worth giving the thermostat housing a quick once‑over. Look for white or pink crusty staining (dried coolant), dampness around the joint, or perishing hoses at the spigot. Because the housing is typically alloy, it’s tough, but gaskets and O‑rings can flatten with age, and road grime can encourage corrosion at the mating face.

• Common symptoms of housing or thermostat issues: slow warm‑up, fluctuating temp gauge, poor heater output, coolant smell or stains near the housing, or an engine light with a P0128 code.
• Good practice during coolant changes: inspect the housing face, renew the thermostat O‑ring, and use fresh long‑life coolant that meets Nissan spec.

Replacement is straightforward for a competent home mechanic. With the engine cool, drain enough coolant to drop the level below the housing, remove the lower radiator hose and housing bolts, then lift the cover to access the thermostat. Note the thermostat “jiggle valve” orientation (as per the service manual), fit the new unit with a fresh O‑ring, clean the mating surfaces, and reinstall. Refill with the correct coolant, set the heater to hot, bleed air (use the bleed screw if fitted and squeeze hoses), and run the engine until the fans cycle. Recheck the level after the first drive. When tightening bolts, follow the factory torque values from the Serena/MR20DE manual rather than guessing — it prevents warping or leaks.

Look after the thermostat housing during regular coolant services and it’ll look after the Serena, especially on long Kiwi or Aussie road trips where steady temps matter.

FAQ: Where is the thermostat housing on a 2009 Nissan Serena?

It sits low at the front of the engine where the lower radiator hose meets the engine block. Pop the bonnet and trace the lower hose back to the engine — the hose connects directly to the housing.

FAQ: Is the thermostat integrated with the housing on this model?

No. The MR20DE in the 2009 Serena uses a separate thermostat that sits inside the alloy water inlet (thermostat housing) and seals with an O‑ring. You can replace just the thermostat and O‑ring, or the entire housing if it’s damaged or corroded.

FAQ: What coolant should be used and how is air bled after housing/thermostat work?

Use a quality long‑life ethylene glycol coolant that meets Nissan specifications. Refill slowly, set the heater to full hot, and bleed air using the bleed screw if fitted while gently squeezing the upper and lower hoses. Run the engine until the radiator fan cycles, top up the radiator and overflow bottle, and recheck the level after the first drive.