Parts for your 2001 Subaru Forester-Thermostat

2001 Subaru Forester Thermostat — Purpose, Care, and When to Replace

Technical sources including the Subaru Factory Service Manual for the 2001 Forester (EJ-series engines), the Subaru Genuine Parts Catalogue (thermostat and gasket listings), and the Haynes Subaru Forester Service & Repair Manual all confirm this model is fitted with a conventional wax‑pellet engine coolant thermostat. It sits in the lower radiator hose housing on the water pump, and controls coolant flow to keep the engine at the right operating temperature.

On a 2001 Forester, the thermostat’s job is simple but crucial: help the engine warm up quickly, then hold a steady temperature for efficient running. It typically begins to open around 78–82°C and is fully open near the mid‑90s, routing coolant through the radiator when needed. That means better fuel economy, smoother driving, proper heater performance and less wear on cold starts.

As part of routine servicing, it’s smart to give the thermostat some attention whenever the cooling system is opened up. Many owners replace it preventively at major intervals (for example when doing a timing belt and water pump) or every 7–10 years/150,000–200,000 km. Always use a genuine or OEM‑spec thermostat and the correct gasket/seal, cheap pattern parts can stick or run the engine at the wrong temp.

Common signs it’s time for a new thermostat include slow warm‑up, temperature gauge wandering up and down, overheating under load, poor cabin heat, or a top radiator hose that stays cold even when the engine’s hot. Because the Forester’s thermostat lives low on the engine, air pockets after coolant changes can mimic a bad stat—so proper bleeding is essential.

• Location: Under the bonnet, follow the lower radiator hose to the water pump housing—two small bolts hold the thermostat cover.
• Good practice: Replace the gasket, clean mating surfaces, and torque bolts to the factory spec.
• Coolant: Refill with the correct Subaru‑approved coolant mix (by volume in litres to suit your climate) and bleed the system thoroughly.
• Tip: Pair a new thermostat with a fresh radiator cap and, if advised for your market, the Subaru cooling system conditioner when addressing known head‑gasket concerns.

For a driveway job, expect 30–60 minutes with basic hand tools and a drain pan. If the system’s been overheating or there’s any doubt about coolant condition, get a pressure test and consider a pro inspection—sorting the thermostat early can save the rest of the cooling system from copping it later.

Popular questions about the 2001 Subaru Forester thermostat

What temperature thermostat does a 2001 Subaru Forester use?

Most EJ‑series 2001 Foresters use a thermostat that starts opening around 78–82°C and is fully open near the mid‑90s. Always match the spec printed on the genuine part or an OEM‑equivalent for your market.

Where is the thermostat located on a 2001 Forester?

It’s mounted at the engine end of the lower radiator hose, in the water pump outlet housing. Access is from the front of the engine bay, some coolant needs to be drained before removing the two housing bolts.

Should the thermostat be replaced with the water pump or coolant service?

Yes, it’s a good idea. Replacing the thermostat whenever the cooling system is open—especially during a timing belt/water pump job—adds little time and helps ensure stable operating temps and long engine life.