Parts for your 2018 Toyota Vitz|yaris-Thermostat

2018 Toyota Vitz/Yaris Thermostat: what it does and how to look after it

Technical sources confirm the 2018 Toyota Vitz/Yaris (XP130 series across KSP130/NSP130/NCP131/NHP130 variants) is fitted with a conventional engine coolant thermostat. The Toyota Workshop Repair Manual for the Vitz/Yaris includes Cooling System – Thermostat inspection, removal and installation procedures, and the Toyota Electronic Parts Catalogue lists a thermostat sub‑assembly housed in the water inlet on engines such as 1KR‑FE (1.0L), 1NR‑FKE (1.3L), 2NR‑FKE (1.5L) and 1NZ‑FXE (hybrid). These factory documents also specify the thermostat’s wax‑pellet design and an opening temperature in the mid‑80s °C range, confirming the part is relevant and serviceable on this model year.

On the 2018 Vitz/Yaris, the thermostat’s job is simple but vital: get the engine up to operating temperature quickly, then hold it steady. That helps fuel economy, keeps emissions low, and protects the engine from both cold wear and overheating. It sits in the water inlet housing where the lower radiator hose meets the engine, directing coolant flow based on temperature.

It’s not normally a scheduled replacement item, but it should be checked whenever cooling system work is done or if there are symptoms. Typical signs include slow warm‑up, a temp gauge that sits low or suddenly spikes, the cabin heater going cold at speed, the radiator fans running more than usual, or a check engine light with a P0128 code. Any coolant seepage around the thermostat housing or crusty deposits are also a cue to act.

When replacement’s due, use a quality thermostat that matches the original spec and always fit a new seal or gasket. Pair the job with fresh Toyota Super Long Life Coolant (pink, premixed) and bleed the system carefully: heater on hot, steady revs, and top up as air purges. It’s smart to inspect the housing, clamps and hoses at the same time. Tighten fasteners to the workshop manual torque spec and recheck levels after the first few drives.

• Good practice during servicing: pressure‑test the cooling system, verify fan operation, and confirm the thermostat opens by monitoring hose temperatures or with a scan tool.
• Typical intervals for coolant on these cars are long (years rather than months), but the thermostat should be replaced if there’s any doubt, especially on high‑kilometre vehicles or after an overheat.

Look after this small part and the Vitz/Yaris stays happy: quick warm‑ups, stable temps, and fewer surprises on a hot Aussie or Kiwi day.

Where is the thermostat on a 2018 Vitz/Yaris?

It’s mounted in the water inlet housing at the engine end of the lower radiator hose. On the NR‑series engines it’s low on the gearbox side of the block. Access usually involves removing the air intake ducting and moving the hose aside.

What are the common symptoms of a failing thermostat?

Slow warm‑up, fluctuating temperature, poor heater performance, or overheating are common. A check engine light with code P0128 (coolant temperature below thermostat regulating temperature) often points to a stuck‑open thermostat.

Do the hybrid Vitz/Yaris models use a thermostat too?

Yes. The NHP130 hybrid uses a thermostat in the engine cooling circuit, along with additional valves and an electric pump. The basic checks and replacement principles are similar, but bleeding can take longer due to the hybrid plumbing.