2016 Subaru Forester Serpentine Belt Routing & Part Numbers

As an ASE-certified master technician, I’ve seen plenty of 2016 Subaru Foresters come through the shop for routine maintenance. The serpentine belt system on the 2.5L FB25 engine (the most common engine option for this model year) is relatively straightforward, but having the right part numbers and routing path is critical for a smooth repair.

Below is your comprehensive reference guide for servicing the 2016 Subaru Forester drive belt system.

Quick answer

• Engine Fitment: 2.5L 4-Cylinder (FB25)
• Belt Length: 65.6 inches
• Rib Count: 6-rib
• OEM Belt Part Number: 23780AA010
• Aftermarket Belt Cross-References: Gates K060656, Dayco 5060655, Continental Elite 4060655
• Auto-Tensioner Assembly Part Number (OEM): 23769AA040
• Idler Pulley Part Number (OEM): 23770AA070

(Note: The 2.0L Turbo FA20 engine uses a slightly different belt configuration; always verify with your parts supplier using your VIN if you have the XT model).

Belt routing

Because we cannot render a physical image here, follow this text-based step-by-step description of the routing path. Pro-tip: Always photograph your existing belt routing with your smartphone before you remove it!

The 2016 Forester features Electric Power Steering (EPS), so there is no power steering pump on the belt drive. The routing for the 2.5L engine is as follows:

1. Start at the bottom center by looping the ribbed side of the belt around the Crankshaft Pulley.
2. Bring the belt straight up the left side (passenger side) to the ribbed A/C Compressor Pulley.
3. Route it across the top, passing under the smooth Idler Pulley.
4. Wrap the ribbed side over the top of the Alternator Pulley.
5. Route it straight down from the alternator to wrap around the Water Pump Pulley.
6. Finally, pull the belt underneath the smooth Auto-Tensioner Pulley (located just above the crankshaft) before connecting back to the starting point.

How to replace the serpentine belt

Replacing the serpentine belt on a 2016 Subaru Forester can typically be done from the top of the engine bay without needing to lift the vehicle.

1. Locate the automatic tensioner assembly on the front of the engine block.
2. Using a dedicated serpentine belt tool or a long-handled 3/8" breaker bar with a 14mm socket, place the tool on the tensioner pulley bolt.
3. Rotate the tensioner counterclockwise (towards the driver's side) to relieve tension on the belt.
4. Slip the old belt off the easiest accessible pulley (usually the alternator or upper idler).
5. Carefully release the tensioner back to its resting position.
6. Remove the old belt and route the new belt following the steps in the "Belt routing" section above. Leave the tensioner or alternator for last.
7. Rotate the tensioner counterclockwise again, slip the new belt onto the final pulley, and slowly release the tensioner to apply pressure.
8. Double-check that all ribs are properly seated in the grooves of the grooved pulleys before starting the engine.

Replacement interval

Subaru generally recommends inspecting the serpentine belt every 30,000 miles or 30 months. However, total replacement is highly recommended between 60,000 and 90,000 miles. If you are replacing a high-mileage belt (approaching 100,000 miles), it is best practice to replace the automatic tensioner and idler pulley at the same time, as the bearings in these components often fail shortly after a new, tighter belt is installed.

Signs of a failing belt or tensioner

Don't wait for the belt to snap and leave you stranded. Watch out for these common warning signs:

• Squealing or Chirping Noises: Usually worse on cold mornings or when the A/C compressor engages. This indicates belt slip or a weak tensioner spring.
• Visible Wear: Look for cracks, fraying edges, or chunking (missing pieces of the ribs) on the underside of the belt. Modern EPDM belts might not crack like older neoprene belts, so check for depth wear in the ribs.
• Accessory Issues: Dimming headlights, a battery warning light on the dash, or sudden spikes in engine temperature can indicate the belt is slipping over the alternator or water pump.
• Tensioner Rattle: If the tensioner bounces excessively while the engine is running or makes a grinding bearing noise, the assembly is failing.

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