Parts for your 2013 Subaru Forester-Radiator cap

2013 Subaru Forester radiator cap — purpose and service advice

Per Subaru’s Factory Service Manual (Cooling section) for the 2013 Forester SH/SJ and the Subaru global parts catalogue, this model is built with a pressure radiator cap (or, on turbo variants, a pressure cap on the header/expansion tank). Non‑turbo FB25 models use a cap on the radiator filler neck, turbo models use a cap on the pressurised header tank that feeds the radiator. So yes — a radiator cap is relevant and fitted to the 2013 Subaru Forester.

The cap’s job is more than just a lid. It seals the cooling system and holds a set pressure so coolant can run hotter without boiling, improving heat transfer and preventing localised hot spots. A secondary vacuum valve in the cap draws coolant back from the overflow bottle as the engine cools under the bonnet, keeping the system full and air out. Typical Subaru specifications for 2013 models are 108 kPa (1.1 bar) for non‑turbo and about 137 kPa (1.4 bar) on turbo header tanks — check the label on the cap and the FSM to match your exact variant.

As part of routine servicing, the radiator cap deserves a quick once‑over. A weak spring, cracked rubber seal, sticky valve, or a nicked filler‑neck seat can all cause pressure loss, hard‑to-trace coolant disappearances, or overheating on steep Kiwi hills or hot Aussie days. Always remove the cap only when the engine is stone cold, use a rag and open slowly to avoid a faceful of hot coolant.

• Inspection habit: At each service (10,000–15,000 km), check the cap’s rubber gasket for cracks or flattening, make sure the spring snaps back, and confirm the vacuum valve moves freely. Look for white crust around the neck — that hints at leakage.
• Replacement timing: Many shops replace caps preventatively about every 5 years/100,000 km, or immediately if a pressure test shows it won’t hold its rated kPa. Caps are inexpensive, and a fresh one can save a head‑scratching overheat.
• Use the right rating: Stick to the Subaru‑specified pressure for your engine. Don’t mix a higher‑pressure turbo cap onto a non‑turbo radiator (or vice versa). Genuine or OE‑quality caps are best.
• After fitment: Top up with the correct Subaru coolant, bleed air properly, check the overflow hose for splits, and recheck levels after a couple of drives.

Whether it’s on the radiator neck (FB25) or the pressurised header tank (XT turbo), a healthy cap keeps the 2013 Forester’s cooling system stable, reliable, and ready for long kilometres.

Popular questions about the 2013 Subaru Forester radiator cap

What pressure rating cap does a 2013 Forester use?
Most non‑turbo FB25 models use a 108 kPa (1.1 bar) cap on the radiator. Turbo variants typically use about 137 kPa (1.4 bar) on the pressurised header tank. The exact spec is printed on the cap and listed in the Subaru FSM and parts catalogue for your VIN.

How often should the radiator cap be replaced?
Inspect it every service and replace around 5 years/100,000 km, or sooner if testing shows it won’t hold pressure, the seal is damaged, or there are signs of leakage. It’s cheap insurance against overheating.

What are the signs of a failing radiator cap?
Unexplained coolant loss, overflow bottle not returning coolant to the system as it cools, collapsed hoses after shutdown, overheating in traffic, or white crust around the filler neck all point to a weak or leaking cap.