Parts for your 2018 Toyota Hilux-Radiator cap

2018 Toyota Hilux radiator cap — fitted, functional and worth a look

Based on Toyota’s 2015–2020 Hilux (AN120/AN130) workshop information and owner’s manual guidance for the cooling system, plus Australian parts catalogues commonly listing a 1.1 bar (approx. 108 kPa) pressure cap for this model, the 2018 Toyota Hilux is fitted with a radiator cap. The cap sits on the radiator neck, while the adjacent overflow bottle is non‑pressurised. Those sources specify a pressure-type cap and warn against opening it when hot, confirming the part is used and relevant on this ute.

The radiator cap on a 2018 Hilux does more than just seal the top tank. It’s a pressure regulator that raises the coolant’s boiling point, helps purge expanding coolant to the overflow bottle when hot, and draws coolant back as the system cools. When it’s working properly, the engine runs at the right temperature, the heater behaves, and the cooling system stays clean and stable under load — whether it’s towing the trailer or crawling in the high country.

As part of regular servicing, it’s smart to give the cap a once‑over. A genuine or quality 1.1 bar cap matched to the vehicle is the go, the rating is stamped on the cap itself. Under the bonnet, look for cracked or flattened rubber seals, a sticky vacuum valve, corrosion around the spring, or dried pink/white crust near the neck — all signs the cap’s not holding pressure. A workshop can pressure‑test the cap alongside a cooling system test, it’s quick and tells the story straight away.

Replacement is affordable and preventative. If there’s any overheating history, random coolant loss, soft hoses after a hot run, or the cap fails a test, fit a new one. Always start with a cold engine, use a rag when opening, and refill with the correct Toyota Super Long Life Coolant mix after any work. Pairing a fresh cap with on‑schedule coolant changes keeps electrolysis and scale at bay, which protects the water pump, heater core and radiator tubes.

• Check the cap at every service or 20,000 km.
• Replace at the first sign of seal wear, spring weakness, or contamination.
• Match the pressure rating and neck style to the Hilux radiator.

Popular questions

What pressure radiator cap does a 2018 Hilux use?
Most 2018 Hilux models use a 1.1 bar (approx. 108 kPa) pressure cap. The correct rating is stamped on the cap. For absolute certainty, match it to the VIN or check the cooling system section of the owner’s manual and the parts catalogue.

Where is the radiator cap on a 2018 Hilux?
It’s mounted on the radiator’s top tank under the bonnet. The nearby translucent bottle is the overflow/reservoir and is not pressurised. Only the cap on the radiator neck is the pressure cap.

Is it safe to open the radiator cap when the engine’s hot?
No. Always wait until the engine is completely cool. Opening a hot pressurised cap can release scalding coolant and steam. If urgent, wrap the cap with a thick rag and release it a notch at a time, but best practice is to let it cool fully first.