🔧 WRX - Serpentine Belt Replacement

The serpentine belt (also called the accessory drive belt) spins your alternator and A/C compressor. Replacing it is mostly about safely releasing the spring-loaded belt tensioner, swapping the belt, and confirming the routing is correct.

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

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⚠️ Safety & Precautions

• ⚠️ Work on a cold engine; hot pulleys can burn you.
• ⚠️ Keep fingers/clothes clear of the belt path; the tensioner is spring-loaded.
• ⚠️ Do not start the engine until you’ve double-checked belt routing on every pulley.
• ⚠️ Battery disconnect is not required, but remove the key and keep it away from the car while working.

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🔧 Required Tools

You'll need the following tools for this repair:

• 14mm socket
• 3/8" drive ratchet
• 3/8" drive breaker bar (18"-24")
• 10mm socket
• Flat-blade screwdriver
• Trim clip removal tool
• 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, put the transmission in 1st gear, and set the parking brake.
• Open the hood and let the engine cool fully.
• Take a quick photo of the belt routing before removal (or use the routing diagram sticker if present).

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Create working room at the front of the engine

• Remove the plastic air inlet/snorkel (if equipped) using a trim clip removal tool for the push-clips.
• If there are small bolts holding the snorkel, remove them with a 10mm socket.
• More space = easier belt install.

Step 2: Locate the belt tensioner

• Use a flashlight and look at the front of the engine where the belt runs.
• Find the spring-loaded tensioner arm; it has a hex point for a tool to rotate it.
• A “tensioner” is the spring-loaded part that keeps the belt tight automatically.

Step 3: Release belt tension

• Put a 14mm socket on the tensioner’s hex and attach a 3/8" drive breaker bar.
• Rotate the tensioner clockwise to relieve belt tension.
• While holding the tensioner rotated, slide the belt off the nearest easy pulley (usually the alternator pulley) by hand with mechanic gloves.
• Slowly let the tensioner return to its resting position (do not let it snap back).

Step 4: Remove the old belt

• Pull the belt out from around the remaining pulleys by hand.
• Inspect each pulley face as you go (look for wobble, chips, or heavy rust).

Step 5: Route the new belt

• Match the new belt to the old belt length and rib count before installing.
• Route the belt around the pulleys following your photo/diagram, leaving the easiest pulley for last.
• Make sure all ribs sit fully in the ribbed pulleys (no rib “hanging off” an edge).

Step 6: Apply tension and finish installation

• Use the 14mm socket and 3/8" drive breaker bar to rotate the tensioner clockwise again.
• Slip the belt onto the last pulley by hand, then slowly release the tensioner.
• Do a final visual check with a flashlight: belt centered on every pulley and fully seated in the grooves.

Step 7: Reinstall removed intake pieces

• Reinstall the snorkel/ducting using the trim clip removal tool (to align clips) and tighten any bolts with a 10mm socket.
• Use a flat-blade screwdriver to snug any hose clamps you loosened.

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✅ After Repair

• Start the engine and let it idle for 30-60 seconds while you watch the belt.
• Listen for squeal or ticking; shut the engine off immediately if the belt walks off a pulley.
• Recheck belt seating once more after a short 5-10 minute drive.

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💰 DIY vs Shop Cost

Shop Cost: $150-$250 (parts + labor)

DIY Cost: $30-$70 (parts only)

You Save: $80-$220 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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