Parts for your 2012 Subaru Forester-Drive belt tensioner

2012 Subaru Forester drive-belt tensioner — what it does and when to sort it

Yes, the 2012 Subaru Forester uses a drive-belt tensioner. On FB25 models (the common 2.5-litre non‑turbo), there’s an automatic spring-loaded tensioner for the main 6‑rib accessory belt that drives the alternator and water pump. The A/C runs a separate stretch-fit belt without a tensioner. On EJ255 turbo models, accessory belts are tensioned via a dedicated tensioner/idler setup. This arrangement is documented in the Subaru Workshop Manual for 2012MY Forester (Engine > Drive Belt) and the Subaru parts catalogue, which both show a belt tensioner assembly for the main accessory drive, while the A/C stretch belt is listed as tensioner‑less on FB engines.

The tensioner’s job is to keep steady tension on the belt as it wears and as the engine loads change. That means consistent charging, reliable cooling, and quieter running under the bonnet. A weak or seized tensioner can let the belt slip, squeal, or wander, and in the worst case can lead to overheating or a flat battery.

As part of regular servicing, it’s smart to give the tensioner and belts a once‑over at each service interval:

• Spin and feel the pulley for roughness, listen for bearing growl.
• Watch the arm with the engine running — it should move smoothly without jittering.
• Check belt tracking, it should sit squarely on the ribs with no fraying.
• Look for belt glazing, cracking, or contamination from oil/coolant.

Replacement is typically condition‑based rather than strictly by kilometres, but many workshops will see tensioners due somewhere around 120,000–180,000 km or at the second belt replacement. If there’s noise, visible wobble, or poor tension, don’t muck about — replace the tensioner and belt together. On FB25 models, note the A/C stretch belt is a one‑time-use item and needs the correct installation tool, there’s no adjuster to wind up. Always follow the Subaru workshop procedure for routing and torque specs to avoid misalignment or bearing damage.

These details align with the Subaru Service Manual (2012MY Forester, H4 engine, Drive Belt section) and Subaru parts cataloguing for 2012 Forester FB25 and EJ255 variants.

Popular questions

Does a 2012 Forester actually have a belt tensioner?
Yes. The main accessory belt uses a tensioner. On FB25 engines the A/C uses a separate stretch-fit belt without a tensioner, but the alternator/water‑pump belt is tensioned automatically. EJ255 turbo models use a tensioner/idler arrangement for their accessory belts.

How often should the tensioner be replaced?
There’s no fixed kilometre rule from Subaru, replace it when noisy, rough, misaligned, or failing to hold tension. Many techs see them due around 120,000–180,000 km or with the second belt change, but condition is king — inspect at every service.

What are the symptoms of a crook tensioner?
Belt squeal on start-up, flickering charge light, overheating in traffic, visible belt flutter, or a rattly/rumbling pulley are all red flags. Any of these under the bonnet is a cue to check both belt and tensioner straight away.