Parts for your 2018 Nissan Pathfinder-Radiator cap

2018 Nissan Pathfinder radiator cap: what’s fitted and why

Based on Nissan’s own technical literature for the R52-series Pathfinder, a traditional radiator-mounted cap is not used on the 2018 model. The Nissan Electronic Service Manual (R52, 2018) in the CO (Cooling System) section specifies a sealed, pressurised reservoir (degas bottle) as the system’s fill point and pressure control. The 2018 Owner’s Manual coolant check procedure likewise refers only to the coolant reservoir cap, not a cap on the radiator itself. Nissan parts catalogues for the R52 list a pressure cap for the reservoir, with no separate radiator cap shown on the radiator assembly. Put simply: there’s no radiator cap on the radiator of a 2018 Pathfinder, the pressure cap lives on the coolant reservoir.

Why don’t they use a traditional radiator cap any more? It’s a modern cooling-system layout designed to improve reliability and thermal control while simplifying servicing.

1. Higher fill point: Putting the pressurised cap on a remote reservoir raises the system’s fill level above the engine and radiator, helping purge air and reduce hot spots.
2. Better air separation: A degas-style bottle continuously bleeds air out of the coolant, improving temperature stability under load.
3. Packaging and safety: With the cap moved off the radiator, there’s cleaner front-end packaging and one less potential leak point up front.
4. Consistent pressure control: The single reservoir cap manages system pressure and overflow/return neatly, aiding long-term durability.

For owners and workshops, that means “radiator cap” talk can be a bit misleading for this model. If the cap needs attention, they’ll be working on the coolant reservoir cap. Sensible checks during servicing include inspecting the reservoir cap seal for nicks or flattening, confirming the spring action feels firm, and ensuring the bottle neck is clean so the cap can seal properly. Only remove the cap when the engine is cold, and use the coolant type and pressure rating specified by Nissan for the R52—don’t mix coolants or fit a random aftermarket cap with the wrong kPa/psi rating.

If there are signs like repeated coolant loss, collapsed hoses after cool-down, or overheating with no visible leaks, a weak reservoir cap can be one of the first, easy-to-test suspects. Replacing a tired cap with the correct-spec unit is inexpensive insurance on the 2018 Pathfinder’s V6 cooling system.

• Where is the radiator cap on a 2018 Nissan Pathfinder?
  On this model there’s no cap on the radiator itself. The pressure cap is on the coolant reservoir (degas bottle), which is the only place owners should open the system for topping up—always when cold.
• What cap pressure does the 2018 Pathfinder use?
  Nissan specifies a pressurised reservoir cap in the typical passenger-vehicle range (around 100–110 kPa/14–16 psi). Always check the label on the fitted cap or the service manual for the exact spec for the vehicle’s VIN.
• How can they tell if the reservoir cap is failing?
  Look for coolant stains around the cap, hoses that collapse as the engine cools, recurring coolant loss without an obvious leak, or gradual overheating under load. If any of these show up, test or replace the cap with the correct-spec unit.