Parts for your 2011 Subaru Impreza-Radiator cap

2011 Subaru Impreza radiator cap — purpose, upkeep, and when to replace

Yes, a radiator cap is used on the 2011 Subaru Impreza. Subaru’s 2011 Impreza Owner’s Manual and workshop manual for the cooling system specify a pressurised cap in the circuit. On non‑turbo models the cap sits on the radiator neck, on WRX/STI turbo models the pressure cap is on the alloy coolant filler/header tank near the top radiator hose, with the radiator itself often un-capped. That layout is standard Subaru practice for this generation.

This little cap does a big job. It seals and pressurises the cooling system (typically around 1.1 bar), which raises the coolant’s boiling point so the engine can run at the right temperature without boiling over on a hot day or a steep Kiwi or Aussie climb. It also has a vacuum valve that lets coolant draw back from the overflow bottle as the engine cools, preventing air from sneaking into the system.

As part of servicing the 2011 Subaru Impreza, the radiator cap deserves a quick check under the bonnet. If the spring weakens or the rubber seals harden, pressure control goes out the window. That can show up as slow coolant loss, hoses that collapse after cool-down, or annoying overheating in traffic. A cap tester can verify the hold pressure, most workshops will do this during a cooling-system service.

• Inspect each service: look for cracked or flattened seals, rusty or crusty deposits, and a sticky valve.
• Replace if it fails a pressure test, after any overheat event, or every few years as cheap insurance.
• Always match the original pressure rating and cap style, don’t “upgrade” to a higher pressure without Subaru guidance.

When replacing, let the engine go stone cold. Wrap a rag over the cap and open it slowly to bleed any residual pressure. Fit the new cap squarely until it clicks to the fully locked position. Top up the overflow bottle to the mark with the correct Subaru-spec coolant (many 2011 cars use blue long-life coolant) and check for leaks after a decent drive.

Whether it’s the radiator neck on a non‑turbo or the header tank on a WRX/STI, a healthy cap keeps the Impreza’s cooling system happy, the heater working properly, and the engine protected right through summer scorchers and alpine mornings.

Popular questions about 2011 Subaru Impreza radiator caps

Where is the radiator cap on a 2011 Impreza?
Non‑turbo models usually have the pressure cap on the radiator neck, just behind the grille. Turbo WRX/STI models place the pressure cap on a separate alloy coolant filler/header tank near the top hose and intake. The translucent overflow bottle has a simple plastic lid and is not the pressure cap.

What pressure rating should the cap be?
Most 2011 Impreza models use a cap around 1.1 bar. Check the number stamped on your existing cap, the under‑bonnet decal, or the service manual for your exact engine. Always replace like‑for‑like to maintain the system’s designed boiling point and hose protection.

How often should the cap be replaced?
There’s no strict time limit, but it should be inspected at every service and pressure‑tested during cooling‑system maintenance. Replace it if it fails testing, shows seal damage or corrosion, or after any overheating incident. Many owners proactively fit a new cap every few years as low‑cost peace of mind.