Parts for your 2011 Honda Stream-Radiator cap

2011 Honda Stream radiator cap – purpose, care, and when to replace

Technical references confirm the 2011 Honda Stream (RN6–RN9) uses a pressurised radiator cap on the radiator. The Honda electronic service manual for the RN-series cooling system specifies a cap near 1.1 bar, and Honda’s parts catalogue lists a “Cap, Radiator (1.1)” for this model. Aftermarket catalogues such as Tridon and Gates also publish direct-fit caps for 2006–2014 Honda Stream variants, reinforcing that a radiator cap is required on this vehicle.

On the Stream, the radiator cap does more than just seal the filler neck. By holding the system at about 1.1 bar, it lifts the coolant’s boiling point, helping the R-series engine stay happy on hot days, long climbs, and in stop–start city traffic. The cap’s spring-loaded valves also manage coolant movement between the radiator and the overflow bottle as the engine heats and cools, and they admit vacuum on cooldown so hoses don’t collapse and air doesn’t sneak into the system.

As part of regular servicing under the bonnet, it’s worth giving the cap a quick once-over. Look for brittle or cracked rubber seals, a sticky or weak spring, corrosion on the seat, or coolant stains around the neck. Typical symptoms of a tired cap include gradual coolant loss, overheating at low speeds, a sweet smell after shutdown, a collapsed upper hose when cold, or lukewarm cabin heat because of air in the circuit.

Only open the cap when the engine is cold, pressure and hot coolant can cause nasty burns. If in doubt, get a shop pressure-test the cap and system. When replacing, stick with the OEM pressure rating (about 1.1 bar) and known brands. Clean the filler neck, ensure the overflow hose is tight and clear, then refill and bleed the system with the correct Honda Type 2 coolant mix, checking for fan cycling and no bubbles.

Handy service tips for the Stream’s cap:

• Test the cap annually or at coolant-change intervals.
• Replace the cap whenever the radiator, thermostat, or water pump is renewed, or at around five years/100,000 km.
• Keep an eye on the overflow bottle level, sudden swings often point to a cap not holding pressure.

Popular questions about 2011 Honda Stream radiator caps

What pressure rating is the correct radiator cap for a 2011 Honda Stream?
The usual spec is around 1.1 bar (about 108 kPa). That’s the rating listed in Honda service information and matched by most reputable aftermarket catalogues. Sticking with the factory pressure keeps the cooling system operating as designed—avoid “uprated” caps unless a professional has advised it for a specific reason.

Where is the radiator cap on a 2011 Honda Stream?
It’s on the radiator neck under the bonnet. The overflow bottle nearby is not pressurised, it’s a reservoir the cap controls via a small hose. Always wait until the engine is fully cool before opening the cap.

How often should the radiator cap be replaced?
Have it inspected at every service and pressure-tested periodically. Many techs will replace the cap preventatively every five years or roughly 100,000 km, or any time the cooling system is being refreshed (radiator, thermostat, water pump, or major hose work).