Parts for your 2004 Subaru Impreza-Drive belt pulley

2004 Subaru Impreza Drive-Belt Pulley — Purpose, Service and Replacement

Yes, a drive-belt pulley is absolutely relevant to the 2004 Subaru Impreza. Technical references including the Subaru 2004MY Impreza Factory Service Manual (STIS) — Mechanical (ME) sections covering Drive Belt, Idler/Tensioner and Crankshaft Pulley — and aftermarket catalogues from Gates and Dayco that show belt routing for EJ20/EJ25 engines, all confirm this model uses accessory drive belts and multiple pulleys (crankshaft, alternator, power steering, A/C, and idler/tensioner). Gregory’s and Haynes manuals for this generation echo the same layout.

On the 2004 Impreza, the crankshaft pulley (often a rubber-damped harmonic balancer) spins the accessory belts that run the alternator, power steering pump and A/C compressor. The water pump is driven by the timing belt on these EJ engines, not the accessory belts. Idler and tensioner pulleys keep the belts aligned and at the right tension, stopping slip and squeal. Many 2004 models use two separate V‑ribbed belts: one for alternator/power steering and another for the A/C.

As part of routine servicing, the drive-belt pulleys and belts deserve a look every service interval (roughly every 10,000–15,000 kilometres, or at least twice a year if the car does short trips). The workshop should check for belt cracking, glazing or frayed edges, and spin the idler/tensioner pulleys by hand to feel for grit or play. Any wobble at the crank pulley, chirping on start-up, belt dust, or a charging-light flicker under the dash points to pulley or belt issues that shouldn’t be ignored.

• Common symptoms: cold-start squeal, intermittent A/C, heavy steering at idle, visible pulley wobble, or a rubber smell/belt dust under the bonnet.
• Service tips: replace noisy idler/tensioner pulleys, re-tension or replace belts that slip, and inspect the crank pulley’s rubber damper ring for cracks or separation.

When it’s time to replace, it’s smart to swap belts and any tired idler/tensioner pulleys together — it saves labour and avoids repeat visits. Use quality OEM-equivalent pulleys and V‑ribbed belts, align the grooves carefully, and set belt tension per the Subaru service manual. The crankshaft pulley bolt must be torqued to the factory specification, a rattle gun alone isn’t a substitute for the correct torque procedure. After fitting, recheck belt tension after a short run-in, especially if the car sees lots of stop‑start city driving. Treated this way, the Impreza’s accessory drive will stay quiet, charge strongly and steer smoothly for years.

FAQs

Does a 2004 Subaru Impreza have one serpentine belt or two belts?
Most 2004 Imprezas with EJ engines run two V‑ribbed belts — one for the alternator/power steering and a separate one for the A/C. This setup is confirmed in the Subaru service manual and common parts catalogues. Some variants may have minor routing differences, but the two-belt arrangement is typical.

How often should the drive-belt pulleys and belts be replaced?
Inspect at every service. Belts are often replaced around 60,000–100,000 kilometres or 4–6 years, but condition trumps mileage. Replace idler/tensioner pulleys if they feel rough, are noisy, or show play. Always follow the service manual’s inspection limits and adjust or replace as needed.

Is it safe to drive with a noisy idler or a wobbling crank pulley?
Not recommended. A failing pulley can shed a belt, leading to loss of charging, heavy steering, or A/C failure. A deteriorating crank pulley (harmonic balancer) can cause vibrations that risk further engine or accessory damage. Get it checked and sorted promptly.