Parts for your 2000 Subaru Forester-Thermostat

2000 Subaru Forester thermostat — what it does and when to replace it

A thermostat is absolutely fitted to the 2000 Subaru Forester and it’s a key part of the cooling system. Technical sources that specify its presence and operation include: the Subaru Forester (SF series, MY1999–2002) Service Manual Cooling System section, which lists the thermostat opening spec at roughly 78–82°C and fully open near 95°C with the air-bleed at the 12 o’clock position, the Subaru parts catalogue for SF Forester with EJ-series engines, which lists a genuine thermostat assembly (commonly noted as 21200-AA072 or a superseding part), and general references like the Haynes Subaru Forester (1998–2008) manual and Gates application guides that catalogue a thermostat for this model. So yes—this Forester uses a conventional wax-pellet thermostat mounted in the lower radiator hose housing at the water pump.

On this Forester, the thermostat helps the engine warm up quickly and then holds coolant near its sweet spot so it runs efficiently, keeps the heater toasty, and avoids both overcooling on the open road and overheating in traffic. If the thermostat sticks open, it’ll take ages to warm up and fuel economy can suffer. If it sticks closed, temps can climb quickly, which is no good for head gaskets or anything else under the bonnet.

There’s no hard replacement interval, but many owners swap it preventatively every 8–10 years or 160,000–200,000 km, or whenever the water pump is being replaced. Most Subaru techs prefer a genuine thermostat with the correct jiggle valve—these engines can be fussy with aftermarket units.

• Common hints it’s time: slow warm-up, temp gauge wandering, weak cabin heat, or sudden overheating.
• Replacement tips: drain coolant, remove the lower hose and thermostat cover, fit the new thermostat with the air-bleed at 12 o’clock, use a fresh gasket/O-ring, and tighten bolts to the service manual spec (don’t overdo it—small bolts into alloy).
• Refill and bleed: heater on HOT, fill slowly with the correct Subaru-approved coolant mix (de‑mineralised water if mixing), run and burp the system, then top up the radiator and overflow once cooled.

A careful bleed makes all the difference on EJ engines. Dispose of old coolant responsibly, it’s toxic to pets. Done right, a fresh OEM thermostat gives years of no‑dramas driving across Aussie and Kiwi conditions.

Popular questions about 2000 Subaru Forester thermostats

Where is the thermostat located on a 2000 Forester?

It sits in the water inlet (thermostat housing) at the front of the engine, where the lower radiator hose connects to the water pump. Access is from underneath or through the front once the splash guard is off and the system is drained.

What temperature should the Forester’s thermostat run at?

The factory spec calls for the thermostat to begin opening around 78–82°C and be fully open near 95°C. On the gauge that usually means sitting around the middle once warmed up, a scan tool will often show high‑80s to mid‑90s in normal driving.

Is it okay to use an aftermarket thermostat?

Many Subaru specialists recommend a genuine thermostat. Aftermarket units can sometimes open at the wrong temperature or flow differently, leading to hunting temps or overheating. If using aftermarket, match the OEM spec exactly and keep the jiggle valve orientation correct.