2017 Subaru Forester: Serpentine Belt Routing & Replacement

Quick Answer

• Belt Length: 1740mm (68.5 inches)
• Rib Count: 6-rib
• OEM Belt Part Number: Subaru 809221230
• Aftermarket Belt Part Numbers: Gates K060685, Dayco 5060685, Continental 4060685
• Auto-Tensioner Part Number: Gates 39401
• Idler Pulley Part Number: Gates 36691

Belt Routing

Before you remove the old serpentine belt, it is crucial to understand its path. We strongly recommend taking a clear photograph of the belt's routing to use as a reference during reinstallation. The belt snakes around numerous pulleys, and a photo will eliminate any guesswork.

The belt routing for the 2017 Subaru Forester with the 2.5L engine is as follows:

1. Starts at the crankshaft pulley at the bottom center.
2. Wraps up and around the A/C compressor on the upper passenger side.
3. Goes down and around the idler pulley located below the A/C compressor.
4. Travels up to the alternator on the top center.
5. Moves to the driver's side, wrapping around the power steering pump.
6. Goes down to the water pump, located below the power steering pump.
7. Finally, returns to the auto-tensioner before going back to the crankshaft pulley.

How to Replace the Serpentine Belt

Replacing the serpentine belt on a 2017 Forester is a manageable task for a DIYer with the right tools. The key is releasing the tension from the auto-tensioner.

1. Safety First: Ensure the vehicle is in park on a level surface with the engine off and cool.
2. Access the Tensioner: The auto-tensioner is located on the lower driver's side of the engine. It has a 14mm hex head cast into its body.
3. Release Tension: Fit a serpentine belt tool or a long-handled 14mm wrench onto the tensioner's hex head. Rotate the tensioner clockwise (towards the driver's side) to release the belt tension.
4. Remove Old Belt: While holding the tensioner, carefully slip the old belt off one of the smooth pulleys, like the idler pulley.
5. Inspect Pulleys: With the belt off, spin the idler and tensioner pulleys by hand. They should spin smoothly and quietly. Any roughness or noise indicates a bad bearing, and the pulley should be replaced.
6. Install New Belt: Following the routing diagram or your reference photo, carefully thread the new belt around all the pulleys, leaving a smooth pulley like the idler for last.
7. Apply Tension: Rotate the tensioner again and slip the belt over the final pulley. Double-check that the belt is correctly seated in the grooves of all ribbed pulleys.
8. Final Check: Start the engine and let it run for a minute to ensure the belt is tracking correctly and running quietly.

Replacement Interval

Subaru recommends inspecting the serpentine belt at regular service intervals (typically every 30,000 miles). While there is no strict replacement schedule, most technicians recommend replacing the belt every 60,000 to 90,000 miles as preventative maintenance, or sooner if signs of wear are visible.

Signs of a Failing Belt or Tensioner

A failing serpentine belt or tensioner will give you several warning signs. Ignoring them can lead to a breakdown, as the belt powers critical components like the alternator, water pump, and power steering.

• Squealing or Chirping Noises: This is the most common symptom, often worse on cold starts or in wet weather. It indicates the belt is slipping.
• Visible Wear: Inspect the belt for cracks, fraying, glazing (shiny spots), or missing ribs.
• Tensioner Noise: A grinding or rattling noise from the engine bay could be a failing bearing in the tensioner or idler pulley.
• Dimming Lights/Charging Issues: If the alternator isn't being spun effectively, you may notice dimming headlights or a battery warning light.
• Overheating: A slipping belt can cause the water pump to underperform, leading to engine overheating.
• Stiff Steering: Reduced power steering assist, especially at low speeds, can be a sign of a slipping belt.

If you're experiencing any of these symptoms, a professional inspection is recommended. Find a trusted shop on Repairius.