Parts for your 2009 Subaru Tribeca-Radiator cap

2009 Subaru Tribeca radiator cap — what it does and how to look after it

Based on Subaru’s factory service information for MY2009 Tribeca (EZ36 cooling system section) and the Subaru parts catalogue for 2008–2014 Tribeca, this model absolutely uses a radiator cap — it’s just not on the radiator neck. Instead, the pressure cap is fitted to a pressurised header tank (coolant reservoir) mounted high in the engine bay. The radiator itself doesn’t have a removable cap. So yes, a “radiator cap” is relevant to the 2009 Subaru Tribeca, but its home is on the upper reservoir, not the radiator.

On the 2009 Tribeca, the radiator cap’s job is to hold system pressure (typically around 108 kPa/1.1 bar for the non‑turbo H6) so coolant boils at a much higher temperature, keeping the engine happy even on long, hot runs. It also has a vacuum valve to pull coolant back from the overflow bottle as the engine cools, so the system stays topped up without air. Because Subaru uses a high-mounted, pressurised header tank on this model, the cap lives there to make the system self-bleeding and easier to fill correctly.

Good servicing includes giving the cap a look every time the coolant is checked. Only ever open it when the engine is stone cold. Inspect the rubber seals for cracks or flattening, make sure the spring feels firm, and check the neck it seals against for nicks or corrosion. If there’s any doubt, replace it with the correct pressure-rated cap specified for the Tribeca — mixing ratings can trigger chronic overheating or push coolant out under load.

Handy signs the cap may be due for replacement:

• Sweet coolant smell, dribbles or staining around the cap or header tank
• Overflow bottle repeatedly emptying or overfilling
• Temperature creeping up on hills or at highway speeds
• Hoses collapsing as the engine cools (vacuum valve not working)

There’s no hard-and-fast interval, but many techs in Australia and New Zealand treat the cap as a low-cost service item: pressure-test it at coolant changes and replace it around 4–6 years or 80–100,000 km, or any time it fails a pressure test. When refitting, clean the sealing surfaces, align the cap tabs properly, and twist fully to the second stop. After any cooling-system work, warm the engine and check for stable level in the overflow bottle and firm upper hoses — both are good signs the cap is doing its job.

Popular questions about the 2009 Subaru Tribeca radiator cap

Where is the radiator cap on a 2009 Subaru Tribeca?
It’s on the pressurised header tank (coolant reservoir) at the top of the engine bay, not on the radiator itself. Subaru designed it this way to make filling and bleeding the system easier and to keep the highest point of the system under pressure.

What pressure rating should the Tribeca’s cap be?
Most 2009 Tribeca H6 models use a cap around 108 kPa (1.1 bar). Always confirm by checking the stamping on the existing cap and the Subaru parts listing for your VIN to avoid under‑ or over‑pressurising the system.

How often should the radiator cap be replaced?
Have it pressure-tested at each coolant service. If the seal is tired, the spring is weak, or it fails a test, replace it straight away. As preventive maintenance, many owners opt to replace it every 4–6 years or 80–100,000 km.