Parts for your 2001 Subaru Forester-Thermostat housing

2001 Subaru Forester thermostat housing: what it does and how to look after it

Yes, the 2001 Subaru Forester uses a thermostat housing. Subaru’s Factory Service Manual for the 2001 Forester (Cooling section) and the Subaru FAST parts catalogue both show the thermostat mounted in the water pump and retained by a two-bolt “water outlet/thermostat cover” – commonly called the thermostat housing. This is the same arrangement across the EJ-series engines fitted to that model year, so the part is absolutely relevant to the vehicle.

On the Forester, the thermostat housing sits low at the front of the engine, behind the lower radiator hose under the bonnet. Its job is simple but critical: it clamps and seals the thermostat in the water pump, provides the outlet neck for the lower hose, and keeps the cooling system leak-free under pressure. If the housing warps, corrodes, or the sealing ring hardens, coolant can seep out and the engine can overheat – not the sort of drama anyone wants.

Servicing is straightforward. Whenever the thermostat is replaced (often done after a cooling system overhaul, overheating incident, or high kilometres), it’s smart to inspect the housing. Look for pitting around the sealing surface, cracks, or a crusty build-up where the hose clamps on. If it’s clean and flat, it can usually be reused, always fit a new thermostat with its correct rubber seal and a fresh hose clamp. If the housing is suspect, replace it – they’re inexpensive insurance.

• Common signs it’s time: coolant smell, pink/white residue around the lower hose, slow leaks, or temperature fluctuations.
• Good practice: use an OEM-spec thermostat (typical Subaru opening temp is around 78°C), new seal, and quality coolant mixed 50/50 with demineralised water.

1. Drain enough coolant to dip below the housing.
2. Remove the two housing bolts (10 mm heads), pull the housing and thermostat.
3. Clean mating surfaces, fit new thermostat and seal in the correct orientation.
4. Refit the housing and torque the bolts to the Factory Service Manual spec (light M6 bolt torque, don’t overtighten).
5. Refill, run the heater on hot, and burp the system. Park nose-up and squeeze the upper hose to help purge air.

A careful refill and burp makes a big difference on Subarus. Top the overflow bottle to the correct mark after a test drive and recheck for any weeping at the housing. Look after this little part and the Forester’s cooling system will stay happy for heaps of Kiwi and Aussie kilometres.

Popular questions about 2001 Subaru Forester thermostat housing

Where is the thermostat housing located?
It’s at the front lower area of the engine, bolted to the water pump, where the lower radiator hose connects. Remove the splash guard and follow the lower hose – the two-bolt cover you find is the housing.

Do you have to replace the housing when changing the thermostat?
Not necessarily. If the sealing face is clean and flat and the outlet neck isn’t corroded, it can be reused. Always install a new thermostat and rubber seal, replace the housing only if it’s cracked, warped, or badly pitted.

What torque should be used on the housing bolts?
They’re small M6 bolts and only require light torque. Follow the Subaru Factory Service Manual spec for the exact value and pattern. Over-tightening can distort the cover and cause leaks.