Parts for your 2000 Subaru Legacy-Thermostat

2000 Subaru Legacy Thermostat — what it does and how to look after it

Yes, a thermostat is fitted and absolutely relevant on the 2000 Subaru Legacy. Subaru’s Factory Service Manual for the 2000 Legacy/Outback (BE/BH) cooling system, along with the Subaru parts catalogue for EJ-series engines used that year, specifies a wax‑pellet thermostat located in the water pump inlet (lower radiator hose outlet). It’s a standard, serviceable part of the cooling system on both 2.0 and 2.5‑litre EJ engines.

The thermostat’s job is to help the flat‑four warm up quickly and then hold a stable operating temperature. When the engine is cold, it stays shut so coolant bypasses the radiator, giving quicker warm‑up, better cabin heat, improved fuel economy, and reduced wear. As temps climb, it opens progressively (typically beginning around the high‑70s °C and fully open in the mid‑90s °C per Subaru specs), sending coolant through the radiator to shed heat. A healthy thermostat stops over‑cooling on the open road and temperature spikes in traffic.

For a 2000 Legacy, the thermostat sits under the bonnet at the bottom of the engine, inside the water pump inlet where the lower radiator hose connects. If the car warms up too slowly, runs cool on the motorway, overheats at speed, swings hot‑to‑cold, or the heater performance is poor, the thermostat may be tired or stuck and worth replacing.

Good servicing keeps it drama‑free. Many owners replace the thermostat proactively when doing a timing belt and water pump, or any time the system is opened for major cooling work. Always opt for a genuine‑spec unit, EJ engines are fussy about flow characteristics and the bypass circuit. Cheap or low‑temp “track” thermostats can cause headaches in daily use.

• Use OEM‑spec thermostat and new seal, install with the jiggle‑pin/air‑bleed at 12 o’clock.
• Clean the mating surfaces and tighten the housing bolts evenly to the factory spec.
• Refill with quality premixed coolant (50/50) suitable for Subaru alloys, avoid tap water.
• Bleed air thoroughly: heater on HOT, radiator cap off while idling until bubbles stop, top up, then recheck after a proper drive and overnight cool‑down.
• Inspect the radiator cap and hoses, weak caps and soft hoses mimic thermostat faults.

Treat the thermostat as a small, inexpensive part that protects a big, expensive engine. Look after it and the Legacy will happily hold temperature from city traffic to alpine passes.

Popular questions about the 2000 Subaru Legacy thermostat

Where is the thermostat on a 2000 Subaru Legacy?
It’s housed in the water pump inlet at the bottom of the engine, behind the outlet where the lower radiator hose connects. Two bolts hold the thermostat cover, remove the lower hose and cover to access the thermostat and seal.

What temperature does the OEM thermostat open?
Per Subaru service data, the Legacy’s thermostat typically begins opening around 78–82°C and is fully open in the mid‑90s°C, ensuring quick warm‑up and stable operating temps across varied driving.

Should they fit a low‑temperature or high‑flow aftermarket thermostat?
For street use in Australia and New Zealand, stick with a genuine Subaru or genuine‑spec unit. Low‑temp or high‑flow versions can upset warm‑up, heater performance, and ECU fuel/ignition strategies, and don’t usually solve cooling issues caused by other faults.