Parts for your 2008 Honda Stream-Thermostat housing

2008 Honda Stream Thermostat Housing: Purpose, Service Tips, and Common Questions

Technical references confirm the 2008 Honda Stream (RN6–RN9, with R18A 1.8L or R20A 2.0L engines) uses a thermostat housing. Honda documentation names it the water outlet/thermostat cover, bolted to the engine and connected to the lower radiator hose. This configuration is detailed in the Honda Stream RN6–RN9 service manual (Cooling System), the Honda Electronic Parts Catalogue for these models, and workshop literature for the related Civic R18A engine, all of which list a thermostat and a dedicated housing/cover assembly.

On this model, the thermostat housing seals the thermostat, directs coolant from the engine to the radiator, and provides a solid mounting point for hoses and, on some variants, a temperature sensor or bleed point. It keeps operating temperatures consistent, which helps fuel economy, cabin heater performance, and engine longevity.

As part of routine servicing on a 2008 Honda Stream, the housing and surrounding hardware are worth a close look. The housings on these engines are typically plastic or alloy, plastic can warp or crack with age and heat cycling, while alloy can corrode if coolant quality is neglected. The O-ring/gasket is a known wear item and should be renewed any time the housing is removed.

Owners and technicians generally replace the thermostat and inspect the housing at around 160,000–200,000 km or 10 years, or sooner if symptoms appear. During the job, it’s smart to:

• Fit a quality thermostat and new housing seal/O-ring.
• Check the housing spigot for nicks and the mating face for pitting, replace the housing if any doubt.
• Clean the mating surfaces and tighten housing fasteners to factory spec.
• Refill with Honda Type 2 blue long-life coolant (premix) and bleed air with the heater on hot, use the bleed screw if fitted.
• Pressure-test the system and inspect hose clamps after the first heat cycle.

Warning signs that point to a suspect thermostat housing include coolant weeping around the lower hose neck, crusty white or green deposits, a sweet smell after parking, overheating, slow warm-up, or an up-and-down temperature gauge. Catching these early prevents bigger dramas like head gasket damage.

Popular questions about the 2008 Honda Stream thermostat housing

Where is the thermostat housing located?
It sits where the lower radiator hose meets the engine. Following that hose back to the block will lead straight to the housing/thermostat cover. Access varies slightly between the R18A and R20A, but the location principle is the same.

Are the 1.8 and 2.0 housings the same?
Functionally they’re the same idea, but part numbers and fittings can differ. Matching by VIN or engine code (RN6/RN7 = R18A, RN8/RN9 = R20A) avoids mix-ups with sensor ports and hose angles.

Is it safe to drive with a leaking thermostat housing?
It’s risky. Small leaks can quickly become big ones, leading to overheating and possible engine damage. If coolant loss or temperature swings are noticed, the vehicle should be inspected and repaired before the next long trip.