Parts for your 2002 Honda Stream-Radiator cap

2002 Honda Stream radiator cap — purpose, fitment and servicing tips

Yes, the 2002 Honda Stream uses a radiator cap and it’s absolutely relevant to the cooling system. Technical sources back this up: the Honda Stream (RN1–RN5) Service Manual includes a “Radiator Cap Inspection/Test” procedure with a specified relief range around 93–123 kPa (about 1.1 bar), and the Honda Electronic Parts Catalogue lists a CAP, RADIATOR (1.1) for RN-series Streams (commonly referenced as P/N 19045-PAA-A01, superseded by equivalent 1.1 bar caps in some markets). AU/NZ parts catalogues from major suppliers also list a 1.1 bar radiator cap for 2001–2005 Honda Stream models.

On this model, the cap sits on the radiator filler neck. It’s a pressure cap that seals the system, raises the coolant’s boiling point, and manages expansion and recovery to the overflow bottle. When the coolant heats up and expands, the cap’s relief valve allows excess coolant to move into the reservoir, as things cool, a vacuum valve draws coolant back, keeping the system topped up and air-free. That pressure control helps prevent boilover on climbs, hot days, or when towing, while the two-way action stops hoses from collapsing as the engine cools.

As part of regular servicing, the radiator cap deserves a bit of attention. A tired cap can mimic bigger problems: intermittent overheating, coolant loss without obvious leaks, a collapsed upper hose after cooldown, or crusty deposits around the filler neck. A workshop can pressure-test the cap to spec with a cooling system tester, if it won’t hold the rated pressure or the vacuum valve sticks, replace it.

Best practice for the 2002 Honda Stream in AU/NZ conditions:

• Use the correct 1.1 bar cap, the wrong rating can trigger overheating or stress hoses and core.
• Inspect the rubber seal and spring every coolant service (about 2 years/40,000 km, or per your maintenance schedule). Replace at the first sign of hardening, cracking, corrosion or weak spring tension.
• Only remove the cap when the engine is cold. If you must open when warm, wrap a rag around it and turn to the first stop to bleed pressure before removal.
• When changing coolant, use the recommended Honda-type long-life coolant (silicate-free), bleed air properly, and confirm the overflow hose is tight and crack-free so recovery works as intended.

Look after the cap and it’ll look after the rest of the cooling system—cheap insurance for the Stream’s alloy engine on long summer runs.

Popular questions about 2002 Honda Stream radiator caps

What pressure rating does the 2002 Honda Stream radiator cap need?
Honda specifies a cap around 1.1 bar (roughly 93–123 kPa relief range). This rating balances boil-over protection with component longevity. Genuine and quality aftermarket options marked 1.1 bar suit the RN1–RN5 Stream.

Stick with the specified rating. Going higher can stress hoses and the radiator, going lower can encourage early boilover and hot-day overheating.

How can they tell if the radiator cap on a Stream is failing?
Common signs include coolant pushing into the overflow and not returning, a collapsed upper hose after cooldown, random temperature spikes at highway speeds, or dried coolant crust near the cap. Sometimes the cabin heater goes weak because air gets pulled into the system.

A quick cap pressure test at a workshop will confirm it. If the seal is perished or the spring is soft, replacement is inexpensive and worthwhile.

Is the cap on the radiator or on the expansion tank?
On the 2002 Stream the pressure cap is on the radiator filler neck. The nearby reservoir is non-pressurised and simply handles expansion and recovery.

Always check that the small hose between the radiator neck and reservoir is clear and secure so the cap’s recovery function actually works.