Parts for your 2006 Subaru Forester-Thermostat housing

2006 Subaru Forester Thermostat Housing

Per the Subaru Factory Service Manual for the 2006 Forester (Cooling System section) and the Subaru FAST/OEM parts catalogue, the EJ25-series engine in this model uses a dedicated thermostat cover, commonly called the thermostat housing. It bolts to the front of the water pump and carries the lower radiator hose. So yes, a thermostat housing is fitted and absolutely relevant for the 2006 Subaru Forester.

This thermostat housing does a few important jobs. It clamps and seals the thermostat in the water pump, provides the outlet for coolant flow to the radiator, and forms a crucial sealing surface via an O-ring or gasket. On Subarus, the thermostat’s bleed (jiggle) valve orientation is important for proper air purging, and the housing ensures the thermostat stays put in exactly the right position. When it’s in good nick, the engine warms up at the right pace, holds steady temperature under load, and avoids drama like overheating or slow warm-up.

As part of routine servicing, it’s smart to inspect the thermostat housing whenever coolant is changed (typically every few years, depending on the coolant type used). Under the bonnet, look for seepage or crusty residue around the lower radiator hose outlet and the two housing bolts. Age, corrosion, or overtightening can warp the housing or flatten the seal, leading to leaks and temperature fluctuations. If there’s any pitting or distortion, replacing the housing along with the thermostat and O-ring is the go-to fix.

Replacement is straightforward for a competent DIYer or workshop. Drain the coolant into a clean container, remove the lower hose, then the two housing bolts. Note the thermostat orientation (bleed valve up), fit a new genuine or high-quality thermostat and O-ring, and clean the mating surfaces carefully—no gouges, no old sealant left behind. Refit the housing and tighten the bolts evenly to the factory torque specified in the service manual, reconnect the hose, refill with the correct long-life, silicate-free coolant mix, and bleed the system. After a test drive, recheck coolant level and look for any weeps around the housing.

Keeping the housing, seal, and thermostat fresh protects the Forester from overheating, heater woes, and premature water pump wear—cheap insurance for a reliable daily, whether it’s city runs or a long Kiwi or Aussie roadie.

• Check for leaks around the lower radiator hose outlet during coolant services.
• Replace the thermostat, O-ring, and housing together if there’s corrosion or warping.
• Use correct coolant and bleed air properly for stable engine temps.

Popular questions about the 2006 Subaru Forester thermostat housing

Where is the thermostat housing located on a 2006 Forester?
It’s mounted on the front of the engine at the water pump, directly behind the lower radiator hose. Two small bolts hold the housing (thermostat cover) in place. Removing that hose exposes the housing and the thermostat seated behind it.

What usually causes leaks at the thermostat housing?
Most leaks come from a flattened or damaged O-ring/gasket, corrosion on the housing or water pump mating face, or uneven/over-tightened bolts. If the surface is pitted or warped, replacing the housing and seal together is the best fix.

Do they need to replace the whole housing, or just the thermostat and seal?
If the housing is clean and flat, a new thermostat and O-ring will usually do the trick. If there’s any corrosion, distortion, or persistent weeping, replace the housing as well to ensure a reliable, long-term seal.