2017 Subaru Outback Serpentine Belt Routing & Length

As an ASE-certified master technician, I frequently service the 2017 Subaru Outback. Known for its reliability and symmetrical all-wheel drive, the Outback relies heavily on its serpentine belt to keep the engine’s accessories running smoothly. Whether you have the 2.5L 4-cylinder (most common) or the 3.6L 6-cylinder engine, maintaining the drive belt system is crucial to avoiding a breakdown.

Below is your comprehensive reference guide for the 2017 Subaru Outback serpentine belt, including part numbers, routing instructions, and replacement tips.

Quick Answer

The following specifications apply to the most common engine option, the 2.5L 4-cylinder (FB25). (Note: Specifications for the 3.6R H6 engine will differ).

• Belt Length: 82.2 inches
• Rib Count: 6-rib
• OEM Belt Part Number: Subaru 23780AA111
• Aftermarket Belt Cross-References: Gates K060820, Dayco 5060820, Continental Elite 4060821
• Auto-Tensioner Assembly Part Number: Subaru 23769AA050 (Aftermarket: Gates 39401)
• Idler Pulley Part Number: Subaru 23770AA070

Belt Routing

Before you begin removing the old belt, I highly recommend using your smartphone to take a few clear photographs of the existing belt routing. This simple step can save you a lot of frustration during reassembly.

For the 2017 Subaru Outback 2.5L, the vehicle utilizes Electric Power Steering (EPS), meaning there is no traditional power steering pump on the accessory drive. The belt routing path is as follows:

1. Start by looping the ribbed side of the belt around the bottom Crankshaft Pulley.
2. Route the belt up and over the Water Pump Pulley (ribbed side contacting the pulley).
3. Continue upward to loop over the top center Alternator Pulley.
4. Bring the belt down the passenger side and around the A/C Compressor Pulley.
5. Finally, route the flat backside of the belt under the Auto-Tensioner Pulley before it returns to the crankshaft.

How to Replace the Serpentine Belt

Replacing the serpentine belt on a 2017 Subaru Outback is a straightforward process that can usually be done from the top of the engine bay.

1. Gather Your Tools: You will need a serpentine belt tool or a standard 14mm socket on a long 3/8" breaker bar to manipulate the tensioner.
2. Release the Tension: Locate the auto-tensioner assembly on the lower passenger side of the engine block. Place your socket on the tensioner pulley bolt. Rotate the breaker bar counterclockwise (or push downward, depending on the tool orientation) to relieve tension on the belt.
3. Remove the Old Belt: While holding the tensioner open, slip the belt off the easiest accessible pulley (usually the alternator). Carefully release the tensioner back to its resting position and pull the old belt out of the engine bay.
4. Route the New Belt: Following your reference photo or the routing description above, snake the new belt around the crankshaft, water pump, and A/C compressor. Leave the alternator for last.
5. Install and Verify: Compress the tensioner again using your breaker bar, slip the belt over the alternator pulley, and slowly release the tensioner. Double-check every pulley to ensure the belt ribs are seated perfectly within the grooves.

Replacement Interval

Subaru recommends inspecting the serpentine belt every 30,000 miles or 30 months. As a general rule of thumb, modern EPDM belts typically last between 60,000 and 90,000 miles. I recommend replacing the tensioner and idler pulleys at the same time you replace the belt, as the bearings in these components often wear out at the same rate.

Signs of a Failing Belt or Tensioner

Don't wait for the belt to snap on the highway. Look out for these common warning signs:

• Squealing or Chirping Noises: A high-pitched squeal on startup or during acceleration usually indicates a loose belt, a weak tensioner, or a misaligned pulley.
• Visible Wear: Look for fraying edges, deep cracks on the ribbed side, or chunking (missing pieces of the ribs). Modern EPDM belts don't crack as easily as older neoprene belts, so you should also check for groove depth wear using a belt wear gauge.
• Accessory Malfunctions: If you notice your A/C blowing warm, the battery warning light flickering on the dash, or the engine running hotter than normal, a slipping or broken belt could be the culprit.
• Tensioner Rattle: If the tensioner bounces excessively while the engine is idling or emits a metallic rattling noise, the internal spring or bearing has failed.

If you don't feel comfortable tackling this maintenance item yourself, don't worry. Find a trusted shop on Repairius.