Parts for your 2018 Honda Cr-v-Radiator cap

2018 Honda CR‑V radiator cap: what it is and where it lives

Referencing the 2018 Honda CR‑V Owner’s Manual (Cooling System/Engine Coolant sections), Honda service literature for the 5th‑gen CR‑V (L15B and R20 engines), and Honda’s electronic parts catalogue, this model absolutely uses a pressure cap for the cooling system. It isn’t on the radiator neck, though. The CR‑V runs a sealed radiator with a pressurised coolant reservoir (deaeration tank), and the pressure cap is fitted to that reservoir. Functionally, it is the “radiator cap” for this vehicle, regulating system pressure and coolant return just as a traditional radiator‑mounted cap would.

This radiator cap’s main job is to hold a set pressure (typically around 1.1 bar/16 psi, check the stamp on the cap for the exact spec) so the coolant’s boiling point is raised, keeping the CR‑V cool on hot summer days and long motorway climbs. It also contains a vacuum valve that lets coolant be drawn back from the reservoir as the engine cools, preventing hoses from collapsing and keeping air out of the system. On the 2018 CR‑V the cap sits on the pressurised reservoir under the bonnet, not on the radiator itself, so the cooling system stays efficient and easier to deaerate.

As part of routine servicing, the cap deserves a quick once‑over. A weak spring, hardened seal, or a sticky valve can cause slow overheating, coolant loss, or gurgling after shutdown. If there are unexplained drops in coolant level, brown crust around the cap, or hoses that collapse when the engine cools, the cap is a prime suspect. Many workshops will pressure‑test the cap with a cooling system tester, it’s a quick way to confirm if it still holds the rated pressure.

• Inspect at every service: check the rubber seal for cracks, the spring action for smooth movement, and the neck for corrosion or debris.
• Replace on condition: fit a quality, correct‑rating cap if the old one fails testing, shows damage, or if there are pressure‑related symptoms. Many owners choose to renew it around major coolant services.
• Only remove when stone cold: twist slowly to the first detent to vent any residual pressure, then remove fully. Clean the neck before refitting.
• After replacement: warm the engine with the heater on, top up to the MAX line as bubbles purge, and recheck the level next morning.

Using the correct spec cap and keeping it healthy is cheap insurance against overheating and head gasket grief, and it keeps the 2018 CR‑V’s cooling system behaving exactly as Honda intended.

Popular questions

Where is the radiator cap on a 2018 Honda CR‑V?
It’s on the pressurised coolant reservoir (deaeration tank) under the bonnet, not on the radiator itself. Honda designed this system so the reservoir and cap handle pressurisation and air separation, while the radiator remains sealed.

What pressure rating cap does a 2018 CR‑V use?
Most Australian and New Zealand–delivered 2018 CR‑V models use a cap around 1.1 bar (16 psi), but always confirm the rating stamped on your existing cap or in service information for your VIN. Using the wrong rating can lead to overheating or unnecessary stress on hoses.

Is it safe to drive with a faulty radiator cap?
Not recommended. A bad cap can cause overheating, coolant loss, or air ingress that’s hard on the water pump and can damage the engine. If symptoms point to the cap, replace or test it promptly and top up with the correct Honda‑approved coolant mix.