Parts for your 2008 Subaru Impreza-Drive belt tensioner

2008 Subaru Impreza drive-belt tensioner — is it actually a thing?

Short answer: for Australian and New Zealand–delivered 2008 Subaru Impreza petrol models, a spring-loaded drive-belt tensioner isn’t fitted, so that specific “drive-belt-tensioner” part isn’t relevant. The EJ-series engines used that year (EJ20, EJ25 and WRX’s EJ255) run conventional multi-rib accessory belts with manual adjustment rather than an automatic tensioner unit.

This isn’t just workshop folklore. Subaru’s factory service manual for MY2008 Impreza (GE/GH platform) shows belt tension being set by the alternator’s pivot/lock bolts and an adjuster screw, with the air-conditioning belt tensioned by a separate idler pulley adjuster. There’s no spring-loaded tensioner illustrated or specified. Parts references back this up too: Subaru’s FAST electronic parts catalogue lists the alternator bracketry and A/C idler components but no accessory belt tensioner assembly for these petrol models. Aftermarket catalogues from Gates and Dayco for 2008 Impreza applications list the belts and idler pulley, and note no automatic tensioner requirement.

Why didn’t Subaru use an automatic tensioner here? The EJ engine layout mounts the alternator high with an integrated adjuster, and the A/C runs its own belt and adjustable idler. It’s a simple, durable setup that keeps costs down and works well with the compact accessory drive on EJ engines. Subaru moved to a single serpentine belt with an automatic tensioner on later FB-series engines, but that came after this generation.

• Alternator/Power-steering belt: tension is set by loosening the alternator pivot and lock bolts, turning the adjuster screw to the correct tension, then re-tightening.
• A/C belt: tension is set via the smooth idler pulley’s adjuster bolt and locknut.

What to maintain instead of a tensioner? Regularly inspect both belts for cracking, glazing, fraying, or chirping on cold start. Spin-check the A/C idler pulley for roughness or play and listen for bearing noise. If squeals appear after rain or on start-up, the belts may be loose or glazed and due for replacement. Many techs in AU/NZ treat these belts as a 60,000–100,000 km or 4–5 year item, sooner if there’s noise or visible wear. Avoid over-tightening, too much tension can wear alternator and power-steer pump bearings.

Note: Some overseas diesel variants (EE20) introduced later use different accessory drive hardware, but that engine wasn’t the norm for AU/NZ 2008 Impreza petrol line-up, which is what this advice covers.

Popular questions

Does a 2008 Subaru Impreza have a drive-belt tensioner?
For AU/NZ petrol models, no. The EJ engines use manually adjusted belts (alternator adjuster and an A/C idler) rather than a spring-loaded automatic tensioner. This is reflected in the Subaru factory service manual, the Subaru parts catalogue, and Gates/Dayco application data.

How are the accessory belts tensioned on a 2008 Impreza?
Loosen the alternator’s lock and pivot bolts, turn the adjuster to set the alternator/power-steer belt tension, then re-tighten. For the A/C belt, adjust the dedicated idler pulley’s screw and locknut. After fitting new belts, it’s wise to re-check tension after a short run-in period.

What wears out instead of a tensioner on these cars?
The belts themselves and the A/C idler pulley bearing are the usual suspects. Look for cracking, glazing, or edge fray on the belts, and listen for a dry, rough-bearing sound from the idler. Replacing a noisy idler or tired belts generally sorts squeals and slippage.