Parts for your 2010 Nissan Serena-Thermostat

2010 Nissan Serena Thermostat: purpose, care, and when to replace

Based on Nissan technical sources — including the factory service manuals (C25/C26 Serena) and Nissan parts catalogues for the MR20DE petrol and M9R diesel engines — the 2010 Nissan Serena is fitted with a conventional wax‑pellet engine coolant thermostat. It’s a core part of the cooling system and absolutely relevant to this model.

The thermostat’s job is simple but critical: it holds coolant in the engine while it warms up, then meters flow to the radiator to keep temperature steady. On Serena engines of this era, the thermostat typically begins to open around 82–88°C, helping the engine reach operating temperature quickly for smoother running, better fuel economy, effective cabin heat, and lower emissions. At cruising speed or in stop–start traffic, it continually trims flow so the gauge stays bang in the middle.

When a thermostat fails, it usually does one of two things. Stuck closed, the Serena can overheat quickly — not ideal on a summer run up the motorway. Stuck open, it takes ages to warm, the heater’s weak, and fuel use can creep up, the ECU may even log a P0128 (coolant temp below thermostat regulating temperature).

• Typical signs it’s due: slow warm‑up, fluctuating temp gauge, “cold” heater at idle, or any overheating.
• Coolant choice: Nissan Genuine Long Life Coolant (blue), mixed 50/50 with demineralised water, is the go‑to for these engines.
• When to replace: thermostats aren’t strictly time‑based, but many owners pair replacement with a major cooling service (around 150–200,000 km) or when doing a water pump/radiator.

Replacement is straightforward for a competent DIYer. With the engine cold, drain enough coolant to drop the level below the housing. On MR20DE models, the thermostat sits in the housing at the engine end of the lower radiator hose, on M9R diesels it’s in the coolant outlet assembly near the gearbox side. Remove the intake ducting as needed, unbolt the housing, note the thermostat orientation (jiggle valve to 12 o’clock if fitted), and install a new thermostat with a fresh O‑ring or gasket. Refit and tighten to factory spec.

Bleeding matters. Set the heater to HOT, fill slowly, open the bleed point if provided, and massage the hoses to purge air. Idle until the fans cycle, top up the radiator and overflow bottle, and check for leaks. Dispose of old coolant responsibly.

• Where is the thermostat on a 2010 Nissan Serena?
  On MR20DE petrol models it’s in the housing at the engine end of the lower radiator hose, typically at the front of the block. On M9R 2.0 dCi diesels it’s integrated in the coolant outlet assembly on the gearbox side, near the EGR cooler. Access often needs the air cleaner duct removed.
• What temperature does it open, and what’s normal?
  The Serena’s thermostat generally starts opening around 82–88°C. In normal use, coolant temperature will sit roughly 85–100°C with the gauge steady at mid‑point.
• Do you have to bleed the cooling system after replacing it?
  Yes. Air locks can cause hot spots, poor heater output, and even overheating. Fill slowly, use the bleed screw if fitted, run the heater on full hot, and verify radiator fan operation before road testing.