Parts for your 2010 Honda Stream-Radiator cap

2010 Honda Stream radiator cap — purpose, care, and when to replace

Technical sources confirm the 2010 Honda Stream (RN6–RN9, R18A/R20A) is fitted with a traditional pressurised radiator cap. Honda’s service literature for the Stream’s Cooling System, the Owner’s Manual cautions about removing the radiator cap only when cool, and the Honda Electronic Parts Catalogue lists a “Cap, Radiator (1.1)” (commonly 19045-PAA-A01, superseded in some listings by 19045-PWA-003) for these models. That makes the radiator cap a relevant, serviceable part on this vehicle.

On the 2010 Honda Stream, the radiator cap does more than just seal the filler neck. It regulates system pressure (around 1.1 bar/108 kPa), which lifts the boiling point of the coolant so the engine can run efficiently without boiling over. Its two-way valve lets expanding coolant move to the overflow bottle when hot and draws it back in as things cool down, keeping the system topped up and free of air pockets.

As part of routine servicing, the radiator cap deserves a quick look. A tired cap can cause sneaky coolant loss, random temperature swings, or even a collapsed upper hose after cool-down. Good practice is to:

• Inspect the rubber seals for cracks or flattening, and check the spring action.
• Pressure-test the cap to the Honda spec (about 108 kPa/1.1 bar) every 2–3 years.
• Replace the cap every 5–7 years or 100,000–120,000 km, or sooner if it fails testing.

When replacing, wait for a stone-cold engine. Wrap a rag around the cap and open it slowly to release any residual pressure. Check the filler neck for corrosion, ensure the overflow hose is snug and not perished, and lightly wet the new cap’s seal with coolant before fitting. Use a quality cap matching Honda’s 1.1 bar rating to avoid over- or under-pressurising the system.

Signs the Stream’s cap may be due include: visible crusting around the neck, gurgling after shut-down, coolant smell, frequent top-ups, hoses that go rock-hard or oddly soft, or overheating at low speeds. Pair cap checks with fresh Honda Type 2 coolant at the recommended interval (often around 5 years/100,000 km in AU/NZ conditions) for a cooling system that just gets on with the job.

FAQs

What pressure rating is correct for a 2010 Honda Stream radiator cap?
Honda specifies roughly 1.1 bar (108 kPa, about 16 psi). Sticking with an OEM cap or a high-quality equivalent at this rating helps keep the boiling point up and the recovery system working properly.

Where is the radiator cap on the 2010 Honda Stream?
It sits on the radiator’s filler neck at the front of the engine bay. On most RN6–RN9 models it’s slightly offset to one side, with a small hose running to the translucent overflow reservoir nearby.

How often should the radiator cap be replaced?
Have it inspected at every service and pressure-tested every 2–3 years. Many owners choose to replace the cap around 5–7 years or 100,000–120,000 km, or immediately if there are cooling issues or test failures.