🔧 Impreza - Serpentine Belt Replacement

The serpentine belt drives accessories like the alternator and A/C. Replacing it restores proper charging and accessory operation and prevents a roadside breakdown from a snapped belt.

Difficulty Level: Intermediate | Estimated Time: 0.5-1.0 hours

Assumption: Your Impreza uses the standard automatic belt tensioner (FB20).

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⚠️ Safety & Precautions

• ⚠️ Work on a cool engine; hot pulleys can burn you.
• ⚠️ Keep fingers/clothes clear of pulleys; pinch hazard when releasing the tensioner.
• ⚠️ Ignition OFF and key away; do not crank the engine during the job.
• ⚠️ Battery disconnect is not required, but avoid shorting tools near the alternator.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm socket
• 1/4" ratchet
• 3/8" ratchet
• 3/8" breaker bar
• 14mm socket
• Flathead screwdriver
• Trim clip remover
• Flashlight
• Mechanic gloves
• Safety glasses

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• Serpentine belt (accessory drive belt) - Qty: 1

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📋 Before You Begin

• Park on level ground, shift to Park, and set the parking brake.
• Open the hood and remove any loose clothing/jewelry.
• Take a clear photo of the belt routing (or locate the routing sticker under the hood). This prevents wrong routing.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Remove the air intake snorkel/duct (for access)

• Use a flathead screwdriver and/or trim clip remover to release the plastic clips/push-pins holding the upper intake snorkel in place.
• If a small bolt is present, remove it with a 10mm socket and 1/4" ratchet.
• Lift the snorkel/duct out and set it aside.

Step 2: Locate the belt tensioner and plan your move

• Use a flashlight to find the automatic belt tensioner (spring-loaded arm with a pulley).
• Identify the hex point you’ll rotate (commonly a 14mm hex on the tensioner arm or the tensioner pulley bolt).
• Automatic tensioner = spring-loaded; it fights back.

Step 3: Release belt tension

• Install a 14mm socket on a 3/8" breaker bar.
• Place the socket on the tensioner hex point, then rotate the tensioner smoothly to relieve belt tension.
• Hold it in the released position (steady pressure).

Step 4: Remove the old belt

• While holding tension off with the 3/8" breaker bar, slip the belt off the easiest-to-reach pulley (often the alternator pulley) by hand with mechanic gloves.
• Slowly let the tensioner return to rest. Don’t let it snap back.
• Remove the belt from the remaining pulleys and pull it out of the engine bay.

Step 5: Inspect pulleys and tensioner (quick check)

• Spin each pulley by hand (engine OFF). It should rotate smoothly and quietly.
• Look for wobble, grinding noise, or cracks on pulley surfaces.
• If a pulley feels rough or wobbly, it likely needs replacement soon. A bad pulley kills new belts.

Step 6: Route the new belt

• Compare the new belt to the old one (length and rib count should match).
• Route the new belt around the pulleys following your photo/routing sticker, leaving one easy pulley for last.
• Make sure the ribs sit fully in the ribbed pulleys and the belt sits centered on smooth pulleys.

Step 7: Apply tension and seat the belt

• Use the 14mm socket and 3/8" breaker bar to rotate the tensioner again and create slack.
• Slip the belt onto the last pulley by hand.
• Slowly release the tensioner so it tightens the belt.
• Re-check every pulley: the belt must be fully seated in every groove.

Step 8: Reinstall the intake snorkel/duct

• Reinstall the snorkel/duct and push-pins using a trim clip remover (as needed) and hand pressure.
• If removed, reinstall the bolt using a 10mm socket and 1/4" ratchet and snug it (do not over-tighten plastic).

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✅ After Repair

• Start the engine and let it idle while you watch the belt for 30-60 seconds.
• Listen for squeal or slapping noises; shut off immediately if the belt walks off a pulley.
• Turn A/C on and headlights on briefly to load the belt, then re-check operation.
• After a short drive, do a quick re-check that the belt is still centered on all pulleys.

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💰 DIY vs Shop Cost

Shop Cost: $180-$350 (parts + labor)

DIY Cost: $25-$60 (parts only)

You Save: $155-$290 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.5-1.0 hours.

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🎯 Ready to get started?

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