🔧 Forester - Serpentine Belt Replacement

Replacing the serpentine belt on your Forester is a good beginner-friendly repair. The belt drives important accessories like the alternator and A/C compressor, so replace it if it is cracked, squealing, glazed, or loose.

Difficulty Level: Beginner | Estimated Time: 30-60 minutes

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⚠️ Safety & Precautions

• ⚠️ Work only with the engine fully off and cool.
• ⚠️ Keep fingers, tools, sleeves, and hair away from the belt path.
• ⚠️ Disconnecting the battery is recommended to prevent accidental cranking while your hands are near the pulleys.
• ⚠️ Your Forester uses separate accessory belts, not one single belt for every accessory. The outer belt must come off first if replacing the inner alternator/power steering belt.

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🔧 Required Tools

You'll need the following tools for this repair:

• 10mm wrench
• 12mm socket
• 12mm wrench
• 14mm socket
• 3/8-inch drive ratchet
• 3/8-inch drive extension
• Torque wrench rated 10-50 Nm
• Flathead screwdriver
• Work gloves
• Safety glasses
• Flashlight

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🔩 Required Parts

HowToo sells all the parts you need for this repair:

• A/C compressor drive belt - Qty: 1
• Alternator/power steering drive belt - Qty: 1

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📋 Before You Begin

• 🚗 Park your Forester on level ground, set the parking brake, and shift into neutral.
• 🔋 Use a 10mm wrench to disconnect the negative battery cable. Negative is usually marked with a minus sign.
• 🔦 Take a clear photo of the belt routing before removal. This gives you a simple reference during installation.
• 🧰 A pulley is a round wheel the belt rides on. The adjusting bolt moves an accessory to tighten or loosen the belt.

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🔨 Step-by-Step Instructions

Follow these steps in order:

Step 1: Open the Hood and Inspect the Belt Layout

• Use a flashlight to look at the front of the engine.
• Your Forester has two front accessory belts: the outer A/C belt and the inner alternator/power steering belt.
• Use your phone or a flashlight to take a belt routing photo before loosening anything.
• Take the photo first.

Step 2: Disconnect the Battery

• Use a 10mm wrench to loosen the negative battery terminal clamp.
• Lift the cable off the battery post and move it aside so it cannot spring back.
• This helps prevent accidental starting while your hands are near the belt area.

Step 3: Loosen the A/C Belt Adjuster Lock Nut

• Use a 12mm socket with a 3/8-inch drive ratchet to loosen the A/C belt tensioner lock nut.
• The A/C belt is the outer belt, closest to the radiator.
• Do not remove the nut completely. Just loosen it enough so the adjuster can move.

Step 4: Loosen the A/C Belt Tension

• Use a 12mm socket with a 3/8-inch drive ratchet and turn the A/C adjuster bolt counterclockwise.
• Keep turning until the A/C belt becomes loose enough to slide off by hand.
• If the belt sticks, use a flathead screwdriver gently at the pulley edge, but do not pry hard against the pulley.

Step 5: Remove the A/C Belt

• Use your hands with work gloves to slide the A/C belt off the pulleys.
• Remove the belt from the engine bay.
• Compare the old belt to the new A/C compressor drive belt to confirm the length and rib count look the same.

Step 6: Loosen the Alternator Pivot and Lock Bolts

• Use a 14mm socket with a 3/8-inch drive ratchet to loosen the alternator pivot bolt.
• Use a 12mm socket or 12mm wrench to loosen the alternator adjuster lock bolt.
• The alternator is the upper front accessory with electrical wiring attached to it.
• Do not remove the bolts. Just loosen them so the alternator can move.

Step 7: Loosen the Alternator Belt Tension

• Use a 12mm socket with a 3/8-inch drive ratchet to turn the alternator adjuster bolt counterclockwise.
• Turn slowly until the alternator/power steering belt becomes loose.
• Use your hands with work gloves to slide the belt off the pulleys.

Step 8: Install the New Alternator/Power Steering Belt

• Route the new alternator/power steering drive belt around the crankshaft pulley, power steering pulley, and alternator pulley.
• Use your belt routing photo to make sure the ribs sit fully in the pulley grooves.
• A ribbed belt must sit squarely in every groove. If it is one groove off, it can shred quickly.
• Check every pulley groove.

Step 9: Tighten the Alternator Belt

• Use a 12mm socket with a 3/8-inch drive ratchet to turn the alternator adjuster bolt clockwise.
• Tighten until the belt has about 1/4-3/8 inch of movement when pressed firmly midway between pulleys.
• Use a 14mm socket and torque wrench rated 10-50 Nm to tighten the alternator pivot bolt to Torque to 25 Nm (18 ft-lbs).
• Use a 12mm socket and torque wrench rated 10-50 Nm to tighten the alternator lock bolt to Torque to 19 Nm (14 ft-lbs).

Step 10: Install the New A/C Belt

• Route the new A/C compressor drive belt over the crankshaft pulley, A/C compressor pulley, and A/C idler/tensioner pulley.
• Use your flashlight to confirm the belt ribs are fully seated in the pulley grooves.
• If the belt will not slip on, use a 12mm socket to loosen the A/C adjuster bolt a little more.

Step 11: Tighten the A/C Belt

• Use a 12mm socket with a 3/8-inch drive ratchet to turn the A/C adjuster bolt clockwise.
• Tighten until the belt has about 1/4-3/8 inch of movement when pressed firmly midway between pulleys.
• Use a 12mm socket and torque wrench rated 10-50 Nm to tighten the A/C tensioner lock nut to Torque to 19 Nm (14 ft-lbs).

Step 12: Reconnect the Battery

• Use a 10mm wrench to reinstall the negative battery cable.
• Tighten the terminal clamp snugly. Do not over-tighten it.
• Make sure no tools are left near the belts before starting the engine.

Step 13: Start and Check Belt Tracking

• Put on safety glasses and start the engine.
• Use a flashlight to watch the belts from a safe distance.
• The belts should run smoothly with no wobble, squeal, or walking off the pulley grooves.
• Shut the engine off immediately if a belt is not tracking correctly.

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✅ After Repair

• ✅ Let the engine idle for 1-2 minutes and listen for squealing.
• ✅ Turn the steering wheel gently left and right while parked. If the belt squeals, the alternator/power steering belt may need slight tightening.
• ✅ Turn the A/C on. If the belt squeals when the compressor engages, the A/C belt may need slight tightening.
• ✅ Recheck belt tension after the first short drive because new belts can settle slightly.
• ✅ Reset the clock and radio presets if they were lost after battery disconnect.

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💰 DIY vs Shop Cost

Shop Cost: $160-$300 (parts + labor)

DIY Cost: $35-$80 (parts only)

You Save: $125-$220 by doing it yourself!

Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.7-1.2 hours.

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