Parts for your 2008 Honda Stream-Thermostat

2008 Honda Stream Thermostat — what it does and when to replace it

Yes, a thermostat is absolutely fitted to the 2008 Honda Stream. Technical references including the Honda workshop manual for the RN6–RN9 Stream (2006–2012) and Honda’s electronic parts catalogue list a wax‑pellet thermostat unit housed in the water outlet/thermostat housing on the engine. It’s a normal part of the sealed, liquid‑cooled system on both the 1.8L (R18) and 2.0L (R20) engines.

The thermostat’s job is to help the engine warm up fast and then hold a steady operating temperature. It stays closed when the engine’s cold so the coolant doesn’t circulate through the radiator, helping it hit the sweet spot quickly. Once it reaches spec (typically begins to open around the low‑80s °C and is fully open in the low‑90s °C), it meters flow to the radiator so the temperature doesn’t wander. That means better fuel economy, cleaner emissions, a stronger heater on chilly mornings, and less engine wear.

For servicing a 2008 Honda Stream, the thermostat isn’t usually a scheduled replacement item, but it should be inspected whenever the cooling system is serviced or if there are temperature irregularities. Many techs in Australia and New Zealand treat it as smart preventative maintenance around major cooling system work or high kilometres. Always use a quality replacement (genuine or OE‑equivalent) with a new O‑ring/gasket, and refill with Honda Type 2 (blue) long‑life coolant. After fitting, bleed the system properly with the heater set to hot to avoid air pockets. The housing bolts are small—tighten to the workshop manual torque spec rather than “by feel” to prevent cracking the housing.

• Common signs the thermostat may be crook:
  • Engine takes ages to warm up, or runs too cool
  • Temp gauge fluctuates or spikes under load
  • Poor cabin heat or a Check Engine Light (often code P0128)
  • Overheating at highway speed or after a hot soak

Replacement is straightforward for a competent home mechanic: let the engine cool fully, drain enough coolant to sit below the housing, remove intake bits for access, swap the thermostat and O‑ring in the water outlet where the lower radiator hose connects, then refill and bleed. If in doubt, a trusted workshop can do the lot quickly and pressure‑test the system to confirm there are no leaks.

• Where is the thermostat on a 2008 Honda Stream?
  It sits inside the thermostat housing (water outlet) where the lower radiator hose meets the engine. On the R18/R20 engines it’s at the front side of the block, low and towards the gearbox end. Access typically involves removing the intake duct and moving a few hoses for space.
• What temperature does the Stream’s thermostat open?
  Honda specs for the RN6–RN9 Stream indicate the thermostat begins to open in the low‑80s °C and is fully open in the low‑90s °C. That range keeps warm‑up brisk while holding a stable operating temperature under load, towing, or summer heat.
• How often should the coolant be changed, and does that affect the thermostat?
  With Honda Type 2 long‑life coolant, the typical interval is up to 10 years/200,000 km for the first change, then about every 5 years/100,000 km. Fresh coolant helps prevent corrosion and scale that can make a thermostat stick. While the thermostat isn’t strictly time‑based, many owners choose to replace it during a major coolant service or if any temperature symptoms pop up.