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2015 Subaru Forester: Serpentine Belt Routing & Replacement

Welcome to the Repairius guide to the serpentine belt system on the 2015 Subaru Forester. As a master technician, I know that a healthy serpentine belt is crucial for keeping your Forester running smoothly. This single belt powers multiple accessories, including the alternator, A/C compressor, and water pump. A worn or failing belt can leave you stranded.

This guide covers both engine options for the 2015 Forester: the 2.5L non-turbo (FB25 engine) and the 2.0L turbo (FA20DIT engine). It's critical to identify your engine, as the belt systems are different.

Quick Answer: Part Numbers & Specs

Before starting any work, confirm part numbers with your VIN at the dealership or with your parts supplier.

For the 2.5L Non-Turbo Engine (FB25)

• Serpentine Belt Length & Rib Count: ~83.5 inches, 6-rib
• OEM Belt Part Number: 809221230
• Aftermarket Belt Cross-References: Gates K060834, Dayco 5060835, Continental 4060835
• Belt Tensioner Assembly Part Number: OEM 23769AA05A
• Idler Pulley Part Number: OEM 23770AA090

For the 2.0L Turbo Engine (FA20DIT)

The 2.0L turbo model uses two separate belts: a main serpentine belt with a tensioner and a separate, stretch-fit belt for the A/C compressor.

Main Accessory Belt:

• Serpentine Belt Length & Rib Count: ~33.3 inches, 4-rib
• OEM Belt Part Number: 809214570
• Aftermarket Belt Cross-References: Gates K040333, Dayco 5040335
• Belt Tensioner Assembly Part Number: OEM 23769AA05A

A/C Compressor Stretch-Fit Belt:

• OEM Belt Part Number: 73323AJ00A
• Aftermarket Belt Cross-References: Gates K040330SF, Dayco 5040330
• Note: Stretch-fit belts require a special installation tool and are designed for one-time use.

Belt Routing

Before you remove the old belt, take a clear photograph of the routing path. This is the most important step to prevent confusion during installation.

2.5L Non-Turbo Belt Routing

The 2.5L engine uses a single belt that snakes around all the pulleys. Starting from the central crankshaft pulley at the bottom, the path is as follows:

1. From the Crankshaft Pulley, the outside of the belt goes up and around the A/C Compressor pulley.
2. The belt travels down to the Alternator pulley.
3. It then wraps up and over the smooth Idler Pulley.
4. Finally, it goes down and wraps under the Automatic Tensioner pulley before returning to the crankshaft.

2.0L Turbo Belt Routing

As noted, this engine has two belts. The main accessory belt is short and easy to identify. From the crankshaft, it routes up to the alternator, then across to the tensioner before returning to the crank. The second belt is a simple loop between the crankshaft pulley and the A/C compressor pulley.

How to Replace the Serpentine Belt

For this job, you will typically need a serpentine belt tool or a long 3/8" drive breaker bar and socket set.

1. Locate the Automatic Tensioner: On both engines, the tensioner is a spring-loaded arm with a pulley that keeps the belt tight.
2. Release Tension: Fit your breaker bar or serpentine belt tool into the designated opening on the tensioner assembly. Rotate the tensioner arm to release the pressure on the belt. This can require a bit of force.
3. Remove the Old Belt: While holding the tensioner in the released position, carefully slip the old belt off one of the smooth pulleys, like the idler or water pump.
4. Install the New Belt: Referring to the photo you took earlier, carefully route the new belt around the pulleys, saving a smooth, easily accessible pulley for last. Double-check that the ribs on the belt are correctly seated in the grooves of each ribbed pulley.
5. Apply Tension: Once the belt is correctly routed, slowly and carefully release the tensioner arm, allowing it to apply pressure to the new belt. Watch to ensure the belt centers itself on the pulleys.
6. Final Check: With the tensioner released, give the belt a final inspection to ensure it's properly seated on every pulley.

Replacement Interval

Subaru recommends inspecting the serpentine belt at regular service intervals. While there is no strict replacement time, it's wise to replace the belt proactively between 60,000 and 90,000 miles. A visual inspection is key. If the belt shows any signs of cracking, fraying, or glazing, it should be replaced immediately, regardless of mileage.

Signs of a Failing Belt or Tensioner

• Squealing or Chirping Noises: This is the classic sign of a slipping, worn, or misaligned belt, especially noticeable on startup or when the A/C is turned on.
• Visible Wear: Look for cracks, glazing (shiny spots), fraying, or missing ribs on the belt.
• Tensioner Noise or Movement: A grinding or rattling noise coming from the tensioner area indicates a failing bearing in the pulley. You may also see the tensioner arm vibrating or bouncing excessively while the engine is running.
• Accessory Malfunctions: If your battery isn't charging (alternator), your A/C isn't cold (A/C compressor), or the engine is overheating (water pump on some models), a failed belt could be the cause.

Performing a serpentine belt replacement is a manageable DIY job for many, but the parts and routing must be correct. When in doubt, professional installation is the best option.

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