Parts for your 2009 Subaru Forester-Drive belt tensioner

2009 Subaru Forester drive-belt-tensioner — what it is, why it matters, and how to look after it

Technical sources confirm the 2009 Subaru Forester is fitted with an automatic accessory drive-belt tensioner. The Subaru Factory Service Manual for the 2009MY Forester (SH) — Engine (ME) section “Drive Belt” for both EJ253 (2.5i) and EJ255 (XT) details a spring-loaded tensioner in the belt routing. Major parts catalogues commonly used by workshops in AU/NZ, including the Gates DriveAlign and Dayco application catalogues for 2008–2012 Subaru Forester, also list an accessory belt tensioner assembly for these engines. This makes the drive-belt-tensioner relevant to servicing on all local petrol variants, with comparable fitment noted on diesel models sold in some markets.

The drive-belt-tensioner on a 2009 Forester quietly keeps the serpentine belt at the sweet spot — not too tight, not too slack — so the alternator, power steering, water pump and A/C all pull their weight. As the belt warms up, stretches and cools again, the spring-loaded arm takes up the change, helping to prevent squeal, slippage and premature wear. It also damps belt flutter at higher revs, which protects bearings and pulleys and keeps charging and cooling reliable on those long Kiwi and Aussie road trips.

As part of routine servicing, it’s smart to give the tensioner a look every service or 20,000 km. With the bonnet up and engine off, check that the belt tracks true and the tensioner arm sits steady. Spin the idler pulley by hand, it should feel smooth and quiet with no wobble. On start-up, a brief chirp on a cold morning can be normal, but ongoing squeal, belt flutter or visible arm chatter points to a tired tensioner. Rusty dust near the pulley, a frayed belt edge or a pulley that’s hot to the touch after a short run are other red flags.

There’s no strict kilometre replacement rule, but many shops see original tensioners due anywhere from 120,000–180,000 km, or earlier if exposed to oil or coolant. If the tensioner’s on the way out, the best practice is to replace the belt at the same time — they age as a team. The job is straightforward with the right spanner to unload spring tension, and following the belt routing diagram under the bonnet. After refitting, make sure the belt is seated in every groove, run the engine briefly, and recheck tracking. Using a quality OEM-equivalent tensioner and belt will save headaches and keep the Forester’s accessories humming along.

• Common signs it’s time: persistent squeal, rattly or rough pulley, belt slipping or glazing, visible arm jitter, or accessories underperforming.

Popular questions

Does a 2009 Subaru Forester actually have a drive-belt tensioner?
Yes. The 2009 Forester (SH) uses a spring-loaded accessory drive-belt tensioner on its serpentine belt system. This is shown in the Subaru service manual’s Drive Belt procedures and is supported by AU/NZ parts catalogues listing a dedicated tensioner assembly for the EJ253 and EJ255 engines.

How often should the tensioner be replaced on a 2009 Forester?
There’s no fixed interval. Inspect it every service, many last 120,000–180,000 km. Replace it if the pulley feels rough, the arm chatters, the belt slips or squeals, or there’s visible misalignment. It’s good practice to fit a new belt when replacing the tensioner.

What happens if the tensioner fails?
If the tensioner can’t hold proper tension, the belt can slip, squeal or come off. That can knock out the alternator, power steering and A/C, and may affect cooling. Continued driving risks overheating or a flat battery. If there are warning signs, sort it before it strands the car.