Parts for your 2013 Subaru Outback-Radiator cap

2013 Subaru Outback radiator cap — what it does and how to look after it

Based on the Subaru Factory Service Manual for the 2010–2014 Outback (Engine Cooling) and Subaru’s parts catalogue, the 2013 Subaru Outback does use a radiator cap (pressure cap). On both the FB25 2.5‑litre and EZ36 3.6‑litre engines the pressure cap is fitted to the pressurised header/expansion tank near the top of the engine, while the radiator itself is capless. The FSM specifies an opening pressure around 108 kPa (1.1 bar), which is printed on the cap, cap specifications in Gates and Dayco catalogues align with this. So yes—this model absolutely relies on a proper radiator cap for correct cooling‑system operation.

On a 2013 Outback, the radiator cap’s main job is to regulate system pressure. By holding pressure to the cap’s rated value, the coolant’s boiling point is raised, helping the Outback keep its cool on long Kiwi highways or in hot Aussie summers. When pressure exceeds the rated limit, the cap lets excess coolant flow to the overflow bottle, as things cool, it draws coolant back, keeping the system topped and largely air‑free. That’s why a healthy cap is small but critical.

As part of routine servicing, it’s smart to inspect the cap anytime coolant is checked or changed. Subaru’s service literature calls for cooling‑system inspections at regular intervals, most techs pair a cap check with coolant changes. Under the bonnet, look for perished rubber seals, a sticky centre valve, weak spring tension, or white crusty deposits around the neck. If in doubt, bin it and fit an OEM‑quality cap with the same pressure rating shown on your original cap label (commonly about 108 kPa/1.1 bar for this model).

Practical tips: only remove the cap when the engine is completely cold. If you hear hissing, wait. Wipe the neck clean before refitting so the seal beds properly. After replacement or a coolant service, use the correct Subaru bleed procedure—filling via the header tank cap, heater on hot, and patiently purging air—to avoid hot spots and temp gauge wander. A tired cap can mimic bigger problems, so keep an eye out for these tell‑tales:

• Coolant smell or staining around the cap or header tank
• Overflow bottle repeatedly overfilling or staying empty
• Upper radiator hose collapsing as the engine cools
• Temperature fluctuations under load or at idle

Swap the cap every few years or at the next coolant change for cheap insurance. It’s a quick win for reliability.

FAQs

Where is the radiator cap on a 2013 Subaru Outback?
It’s on the pressurised header/expansion tank mounted high on the engine bay, not on the radiator itself. Subaru designed this system to make bleeding air easier and to keep the highest point of the cooling circuit under a proper pressure cap.

What pressure rating cap does it use?
Most 2013 Outback models use a cap around 108 kPa (1.1 bar). Always check the rating printed on your existing cap or in the service information for your specific engine, and match it like‑for‑like.

How often should the radiator cap be replaced?
There’s no hard expiry, but inspecting at every service and replacing every few years—or whenever seals look tired, the spring feels weak, or cooling issues appear—is good practice. Many owners pair cap replacement with coolant changes.