Parts for your 2005 Honda Stream-Radiator cap

2005 Honda Stream radiator-cap: purpose, maintenance and when to replace

Per Honda’s own technical literature, the 2005 Honda Stream is built with a pressurised radiator cap. The Honda Stream (RN3–RN5) Service Manual, Cooling System section, details a pressure-type cap fitted to the radiator or a remote filler neck, with a test/relief specification of about 108 kPa (1.1 bar). Honda’s electronic parts catalogue likewise lists a 1.1 bar cap (commonly superseded under part number 19045-PAA-A01/A02) for 2005 Stream variants. So, the radiator-cap is absolutely relevant to this model.

On a 2005 Honda Stream, the radiator cap does more than just seal the top. It controls system pressure so coolant can run hotter without boiling, helps move coolant to and from the overflow bottle as things heat up and cool down, and keeps air out of the circuit. That means steadier temperatures, fewer hot spots, and a happier water pump and heater core under the bonnet.

As part of regular servicing, the cap is worth a quick health check. A tired spring or perished rubber seal can cause hard-to-trace dramas like slow overheating, coolant loss, or hoses collapsing after shut-down. A workshop can pressure-test the cap to spec (about 1.1 bar), if it won’t hold pressure or release smoothly, it’s time for a new one. Many owners choose to replace the cap preventively every 4–5 years or 80–100,000 kilometres, especially in warmer climates or if towing.

• Only remove the cap when the engine is stone cold. Under pressure, hot coolant can cause serious burns.
• Inspect for cracked or flattened seals, a gunky seat, or a weak spring feel. Any doubt—replace.
• Use a quality 1.1 bar cap that matches the original profile, genuine or reputable aftermarket is fine.

Some Streams place the cap on a small filler neck along the upper radiator hose rather than on the radiator tank itself. The translucent overflow bottle is not pressurised, so don’t confuse its lid for the radiator cap. When refilling coolant (Honda Type 2 blue premix is the usual go-to), bleed air as per the manual and confirm the cap is fully seated to the second detent. A sound radiator-cap keeps the system sealed, the gauge steady, and road trips across Aussie and Kiwi summers drama-free.

Popular questions about the 2005 Honda Stream radiator-cap

What pressure radiator cap does a 2005 Honda Stream use?
Most 2005 Honda Stream variants use a 1.1 bar (108 kPa) cap. That pressure suits the engine’s cooling layout and helps lift the boiling point without over-stressing hoses. Matching the original rating is important for stable temps and proper coolant recovery.

Where is the radiator cap located on a 2005 Honda Stream?
Depending on the engine variant, it’s either on the radiator’s top tank or on a small remote filler neck near the upper radiator hose. The overflow bottle cap is not the radiator cap—it isn’t pressurised.

How often should the radiator cap be replaced?
Have it inspected at each coolant service and pressure-tested if there are symptoms. Many owners replace the cap every 4–5 years as cheap insurance, or sooner if there’s overheating, coolant loss, or a failing test result.