Parts for your 1990 Nissan Primera-Thermostat

1990 Nissan Primera thermostat — what it does and how to look after it

The 1990 Nissan Primera (P10) absolutely uses a conventional engine coolant thermostat. This is documented in the Nissan Factory Service Manual (P10 FSM, Cooling System section), the Nissan FAST electronic parts catalogue, and aftermarket guides such as the Haynes Nissan Primera 1990–1999 manual. Across common P10 engines — GA16 petrol, SR20 petrol (DE/Di) and CD20 diesel — the thermostat sits in the water inlet housing on the engine side of the lower radiator hose, and regulates coolant flow based on a wax-pellet element with a specified opening temperature stamped on the part.

In day-to-day driving, the thermostat helps the Primera warm up quickly, then holds a steady operating temperature for good fuel economy, solid heater performance, and long engine life. When it sticks open, the car can take ages to reach temp, when it sticks closed, it can overheat surprisingly fast. That’s why a healthy thermostat is a small part with a big job.

As part of routine servicing, it’s smart to replace the thermostat every few years or around 100,000 km, especially if the coolant service history is a bit unknown. Always match the OEM-specified temperature rating and use a quality unit with the correct jiggle valve and O-ring seal. Fit it with the jiggle valve at the 12 o’clock position to aid bleeding, clean the mating surfaces, and tighten the housing bolts evenly to the factory torque (refer to the FSM).

Pair a new thermostat with fresh, correct-spec coolant mixed to the proper ratio. After refitting, bleed the cooling system carefully: heater on full hot, open the bleed point if equipped, top up slowly, run the engine at fast idle, and squeeze the upper hose to purge air. Recheck the level after a decent drive once it cools.

• Watch for signs it’s due: slow warm-up, temp gauge wandering, poor cabin heat, overheating under load, or fans running constantly.
• Inspect hoses and the radiator cap while you’re there — weak caps can mimic thermostat issues.
• On CD20 diesels, specs differ slightly, but the service approach is the same — follow the FSM for that engine.

Popular questions

Where is the thermostat on a 1990 Nissan Primera?
It’s housed in the water inlet on the engine block, where the lower radiator hose connects. Remove the hose, undo the two housing bolts, and you’ll see the thermostat and its O-ring seal sitting in a recess.

What temperature rating should the thermostat be?
The OEM rating is listed in the Nissan FSM and stamped on the thermostat itself. It typically begins to open in the low‑80s °C range for Primera petrol engines. Always match the factory spec for your exact engine code.

Do you need to bleed the cooling system after changing it?
Yes. Set the heater to hot, fill slowly, open the bleed screw if fitted, then run at fast idle until the fans cycle. Top up as needed and recheck the level once it cools. Proper bleeding prevents airlocks and hot spots.