Parts for your 2010 Subaru Legacy-Drive belt pulley

2010 Subaru Legacy drive-belt pulley — what it does and how to look after it

Yes, a drive-belt pulley is absolutely fitted to the 2010 Subaru Legacy and it’s relevant to routine servicing. Subaru’s 2010 Legacy/Outback Factory Service Manual (V-belt/Front Belt & Pulleys sections), Subaru Technical Information System (STIS), and aftermarket catalogues from Gates and Dayco all show accessory drive pulleys on the EJ25 (2.5 NA), EJ255 (2.5 turbo) and EZ36 (3.6 H6) engines, including the crankshaft pulley (harmonic balancer), alternator, A/C compressor, power steering pump, plus idler and tensioner pulleys depending on engine.

In everyday terms, the drive-belt pulley system transfers the crankshaft’s spin to the bits that keep the Legacy livable — alternator for charging, power steering pump for easy turning, and the A/C compressor for cool air. The crank pulley’s rubber-isolated “harmonic balancer” also dampens vibration, which keeps the engine smooth and protects accessories. On four-cylinder EJ engines there are typically two V‑ribbed belts and multiple pulleys, the 3.6 H6 runs a serpentine layout with an automatic tensioner.

Good servicing means eyeballing and listening. At each service (every 10–15,000 km), check belt rib condition and tension, look for pulley wobble, and spin idler/tensioner pulleys for roughness. Common warning signs include:

• Cold-start squeal, chirps or a growly bearing noise
• Visible pulley misalignment or belt tracking on one edge
• Cracks or glazing on belts, rubber separation on the crank pulley’s balancer

Replacement is straightforward with the right kit. On EJ25 models, there are separate belts for A/C and alternator/power steering, tension is set via adjusters, so don’t over-tighten — too much tension hammers bearings. The EZ36’s serpentine belt is tensioned automatically, if the belt is worn or there’s a chirp, inspect the tensioner and idler pulleys at the same time and replace as a set if needed. Always follow the workshop manual for routing and torque specs, and make sure the crank pulley keyway and bolt are clean and correctly tightened.

Quality parts matter. Stick with reputable OEM or equivalent pulleys and belts, ensure the ribs match the pulley profile, and recheck belt tracking after a short drive. A quiet, steady belt and pulley setup keeps the Legacy charging well, steering light, and A/C frosty — exactly how it should be for Aussie and Kiwi conditions.

Popular questions about 2010 Subaru Legacy drive-belt pulleys

How can someone tell if the noise is a pulley or the belt?
Briefly misting the belt with water under the bonnet can change a belt squeal, but it won’t quiet a rough pulley bearing. If the sound remains or turns into a rumbling/grinding that changes with engine speed, the likely culprit is an idler or tensioner pulley. A mechanic’s stethoscope (or a long screwdriver carefully placed on the housing) can help pinpoint the noisy pulley.

Does the 2010 Legacy use one belt or two, and does that affect the pulleys?
EJ25 models generally run two V‑ribbed belts, while the 3.6 H6 uses a single serpentine belt. The layout dictates which pulleys are present and how they’re tensioned. The H6 relies on an automatic tensioner and dedicated idlers, the EJ typically has manual adjusters. When ordering parts, matching the engine code ensures the right pulley and belt setup.

Should the crank pulley/harmonic balancer be replaced as preventative maintenance?
It’s not strictly time-based, but age, heat, and oil contamination can degrade the rubber isolator. If there’s any wobble, rubber cracking, or a ringing/knock from the front of the engine, it’s wise to replace the balancer. Inspect it at every service and anytime belts are off, especially on higher‑kilometre cars.