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