Parts for your 2018 Toyota Vitz|yaris-Radiator cap

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

Yes, the 2018 Toyota Vitz/Yaris uses a proper radiator cap on the radiator itself, not just a sealed expansion tank. This is confirmed by Toyota’s service literature for the KSP130/NCP131/NSP130 series (Cooling section: Radiator Cap – On‑Vehicle Inspection) and the Toyota Electronic Parts Catalogue, which lists a Radiator Cap Sub‑Assembly (commonly 16401‑31650, approx. 88 kPa/0.9 bar) for 2018 Vitz/Yaris variants. Australian and New Zealand Toyota parts catalogues also show a serviceable cap for this model.

On this Yaris, the radiator cap is a small but crucial bit of kit. It seals and pressurises the cooling system, lifting the coolant’s boiling point so the engine can run at the right temperature without bubbling over on a hot day or a long hill climb. Inside the cap are two valves: a pressure valve that holds pressure to about 0.9 bar, and a vacuum valve that lets coolant return from the overflow bottle as the engine cools. If the cap gets weak, gummy, or the seals harden, the system can lose pressure, pushing coolant out or letting air in. That can show up as higher temps, sloshy heater performance, or crusty pink deposits around the neck.

As part of routine servicing on a 2018 Vitz/Yaris, the radiator cap deserves a quick check. Pop the bonnet when the engine is stone cold and inspect the rubber seal, spring tension, and the little vacuum disk. Any nicks, swelling, or white/pink crust means it’s time for a new one. A workshop can pressure‑test the cap to the specified rating, if it doesn’t hold, replace it. Because it’s inexpensive and absolutely mission‑critical, many techs treat the cap as a preventative replacement item every 4–5 years or around 80–100,000 km, especially in hot climates or if the coolant has been overdue.

• Only remove the cap when the engine is completely cold.
• Use the correct pressure rating (about 0.9 bar/88 kPa as per Toyota specs for this series).
• Pair cap replacement with coolant service (Toyota Super Long Life Coolant) and check the overflow hose for cracks.
• Prefer genuine or quality OEM‑equivalent caps to ensure proper pressure and fit on the radiator neck.

Looked after properly, the cap helps keep the Yaris happy on Kiwi backroads and Aussie motorways alike, preventing boil‑over and maintaining steady, efficient running.

Where is the radiator cap on a 2018 Toyota Vitz/Yaris?

It’s mounted on the radiator’s filler neck at the front of the engine bay, typically on the upper tank near the centre or slightly offset. You’ll also see a translucent overflow bottle nearby with a hose running back to the neck below the cap.

Always check and remove it only when the engine is completely cold to avoid scalding.

What pressure rating should the 2018 Vitz/Yaris radiator cap be?

Toyota specifies roughly 0.9 bar (88 kPa) for this series, as shown in the Toyota repair manual and parts listings for KSP130/NCP131/NSP130 models. Using the correct rating keeps the coolant’s boiling point where it should be and protects hoses and seals.

Match the OEM spec on any replacement cap for proper fit and system performance.

How often should the radiator cap be replaced?

Inspect it at every service and replace at the first sign of weak spring tension, damaged seals, or staining. As a preventative, many owners swap it every 4–5 years or 80–100,000 km, often alongside a coolant change.

Frequent short trips, high heat, or overdue coolant changes can justify earlier replacement.