Parts for your 2013 Subaru Legacy-Radiator cap

2013 Subaru Legacy radiator cap — what it is, where it lives, and when to replace it

Based on technical references, a radiator cap is absolutely relevant to the 2013 Subaru Legacy. The Subaru Service Manual for the 2010–2014 Legacy/Outback cooling system specifies a pressurised cap (approx. 108 kPa / 1.1 bar) as part of the system. Subaru’s parts catalogue for the BM/BR chassis lists a radiator/coolant filler cap for the 2013 model year, and common application guides from major cooling brands list matched caps for this vehicle. On the 2.5-litre FB25, the pressure cap is fitted to the coolant filler tank near the top of the engine, while on some 3.6R EZ36 setups the cap is on the radiator itself. Either way, the Legacy uses a serviceable pressure cap.

On a 2013 Subaru Legacy, the radiator cap isn’t just a lid, it’s a pressure valve that keeps the coolant system sealed and at the right pressure so the coolant’s boiling point is raised. That means better heat control under the bonnet, fewer hot spots, and more consistent cabin heating. It also manages coolant flow to and from the overflow bottle as the engine heats and cools, keeping the system topped up without pulling air in.

As part of routine servicing, the radiator cap deserves a quick once-over. Rubber seals harden with age, springs can weaken, and even a tiny nick on the sealing surface can cause slow leaks or overheating at highway speeds. A cap that’s not holding pressure can mimic a failing thermostat or water pump, so it’s a small, cheap part that can save a lot of head-scratching.

• Check the cap every 20,000–30,000 km or annually, and replace around the 5–7 year mark, sooner if there are signs of trouble.
• Only remove the cap when the engine is stone cold. Under pressure, hot coolant can cause serious burns.
• Inspect the rubber gasket and the spring-loaded valve for cracks, flattening, or corrosion. If in doubt, bin it and fit a new one.
• Use the correct pressure rating (around 108 kPa/1.1 bar for most 2013 Legacy trims) as specified by Subaru. Mismatched pressure can lead to leaks or stress on hoses and the radiator.

If they’re chasing odd coolant loss, gurgling in the heater, or rising temps on long pulls, a fresh, correct-spec radiator cap is an easy first step before digging deeper.

Popular questions about the 2013 Subaru Legacy radiator cap

Where is the radiator cap on a 2013 Subaru Legacy?
On most 2.5-litre FB25 cars, the pressure cap sits on the alloy coolant filler tank high on the engine, not directly on the radiator. Some 3.6R models have the cap on the radiator itself. If they can’t see a cap on the top tank, look for the separate filler neck near the intake.

What pressure cap does a 2013 Legacy use?
Subaru specifies a cap around 108 kPa (about 1.1 bar or 16 psi) for this model range. Sticking with the factory-specified rating helps maintain the correct boiling point and avoids over-pressurising hoses and seals.

What are the signs a radiator cap needs replacing?
Common clues include coolant pushing out into the overflow and not returning, collapsed upper hose after cool-down, slow overheating on climbs, or visible damage to the cap’s rubber seal. If any of these show up, a new cap is inexpensive insurance.