Parts for your 2004 Subaru Legacy-Drive belt tensioner

2004 Subaru Legacy drive-belt-tensioner: what’s actually fitted

Based on technical references — the Subaru Factory Service Manual for the 2004 Legacy/Outback BE/BH (H4 SOHC), the Haynes Subaru Legacy & Outback 2000–2009 manual, and Dayco/Gates application catalogues — the 2004 Subaru Legacy with the common 2.5‑litre EJ25 engine doesn’t use a separate, spring‑loaded drive‑belt tensioner assembly. Instead, it runs two individual multi‑rib belts: one for the alternator/power steering and another for the air‑conditioning. Belt tension is set manually via the alternator’s slotted bracket and adjuster bolt for the alternator/PS belt, and by a dedicated A/C idler pulley with a lock nut and long adjuster bolt for the A/C belt. That’s why many catalogues list “no automatic tensioner” for this model.

Why no drive‑belt tensioner on this Legacy? Subaru’s EJ layout of this era was designed around twin accessory belts with simple mechanical adjustment. It keeps costs down, packaging tidy, and the system robust. It also makes roadside or driveway belt swaps under the bonnet pretty straightforward with basic tools. Note that some later BP/BL models and the six‑cylinder EZ30 setups do use an automatic serpentine tensioner, but that’s a different configuration to the 2004 EJ25 Legacy covered here.

What should owners do instead? Treat belt condition and correct adjustment as normal service items. Inspect both belts for cracks, fraying, glazing, or chirping after cold starts. If replacing a belt, loosen the relevant lock bolts, use the adjuster to set tension to spec (per the Subaru service manual), then re‑tighten the locks. Re‑check tension after the first 100–200 kilometres as new belts bed in. While you’re there, spin the A/C idler pulley by hand — any roughness or noise means the bearing is on the way out and the pulley should be replaced. Avoid over‑tightening, which can overload alternator and idler bearings.

• No spring‑loaded “drive‑belt tensioner” assembly on 2.5L 2004 Legacy, uses manual adjusters.
• Service focus: belt condition, correct manual adjustment, and A/C idler pulley health.
• If the vehicle is a six‑cylinder EZ30 variant, it may have an automatic tensioner — check the exact engine and catalogue listing.

Does a 2004 Subaru Legacy have a drive‑belt tensioner?

On the 2.5‑litre EJ25 models, there isn’t a separate, spring‑loaded drive‑belt tensioner. Tension is set manually using the alternator bracket/adjuster and the A/C idler adjuster. Some six‑cylinder EZ30 variants (more common in Outback or later BP/BL Legacy) do use an automatic tensioner, so engine type matters.

How are the belts adjusted on a 2004 Legacy EJ25?

Loosen the lock bolts, turn the adjuster to achieve the specified tension, then tighten everything back up. Do this for the alternator/PS belt at the alternator bracket, and for the A/C belt at the idler pulley adjuster. Re‑check after a short run as new belts settle. Don’t over‑tighten — that can chew out bearings.

What should be replaced with the belts?

Alongside new belts, it’s smart to assess the A/C idler pulley. If its bearing feels gritty or noisy, replace the pulley. Also check the alternator and power‑steering pulleys for alignment and any wobble before buttoning up.