🔧 Impreza - Serpentine Belt Replacement

The serpentine (accessory drive) belt runs your alternator and A/C compressor. If it’s cracked, glazed, squealing, or loose, replacing it prevents charging issues and overheating from accessory loss.

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

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⚠️ Safety & Precautions

• ⚠️ Let the engine fully cool before working near the radiator fans and pulleys.
• ⚠️ Keep fingers/clothing away from pulleys; never work with the engine running.
• ⚠️ Support plastic clips carefully to avoid breaking the intake snorkel/ducting.
• ⚠️ Battery disconnect is not required for this job.

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🔧 Required Tools

You'll need the following tools for this repair:

• Safety glasses
• Mechanic gloves
• Flashlight
• 10mm socket
• 3/8" ratchet
• 3/8" breaker bar
• 14mm socket
• Trim clip removal tool

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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 and set the parking brake.
• Open the hood and confirm you can see the belt routing diagram (usually on the underside of the hood or radiator support).
• If access feels tight, remove the plastic intake snorkel at the front of the engine bay (it’s the plastic duct that feeds the air box).

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Make room to work (if needed)

• Use a trim clip removal tool to pop up any plastic push-clips holding the intake snorkel.
• Use a 10mm socket and 3/8" ratchet to remove any 10mm bolts holding the snorkel/ducting (if equipped).
• Lift the snorkel out and set it aside.

Step 2: Record the belt routing

• Use a flashlight to clearly see the belt path across all pulleys.
• Take a phone photo of the routing diagram and the current belt routing.
• Photo now saves big headaches later.

Step 3: Release belt tension

• Locate the belt tensioner (spring-loaded arm with a smooth pulley).
• Install a 14mm socket on a 3/8" breaker bar and place it on the tensioner’s bolt head.
• Rotate the tensioner to relieve tension, then slide the belt off one easy-to-reach pulley (usually the alternator at the top).
• Move slowly; the tensioner is strong.

Step 4: Remove the old belt

• With the belt off one pulley, remove the belt from the remaining pulleys by hand.
• Use a flashlight to inspect each pulley groove for built-up rubber or debris.

Step 5: Route the new belt

• Compare the new belt to the old belt length and rib count before installing.
• Route the new belt following the under-hood routing diagram.
• Make sure the ribbed side sits fully in the grooved pulleys, and the smooth side runs on smooth pulleys.
• Use a flashlight to verify the belt is centered on every pulley.

Step 6: Re-apply tension

• Use the 14mm socket with the 3/8" breaker bar to rotate the tensioner again.
• Slip the belt over the last pulley, then slowly release the tensioner.
• Re-check every pulley: the belt ribs must be seated in the grooves with no “half-on” alignment.

Step 7: Reinstall intake snorkel/ducting

• Reinstall the snorkel/ducting.
• Use a 10mm socket and 3/8" ratchet to tighten any 10mm bolts snugly.
• Reinstall push-clips by pressing them back in by hand.

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✅ After Repair

• Start the engine and let it idle for 30-60 seconds while you watch the belt track (stand clear of moving parts).
• Listen for squealing, chirping, or slapping noises. If you hear any, shut the engine off and re-check belt seating.
• Turn A/C on and headlights on briefly to load the belt and confirm it runs smoothly.

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💰 DIY vs Shop Cost

Shop Cost: $150-$300 (parts + labor)

DIY Cost: $25-$70 (parts only)

You Save: $125-$230 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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