Replacing Accessory Belts on a Subaru Impreza
This article will guide you through the replacement of the Alternator/Power Steering belt and Air Conditioning belt for your STI.
Estimated Duration: 20 minutes
Difficulty Level: Novice
My AC belt starting squeaking/slipping after 72K miles. A closer inspection revealed both belts were cracking with age, glazed, brittle and needing replacement.
Remove the Air Intake
Remove the two 10mm bolts
Grasp the intake; pull it away from the fender coupling; remove
Remove the belt cover
Remove the 10mm bolt on the left and the 10mm nut on the far right.
Once these are removed, slip off the cover from the stud on the right side, then pull the cover up to free the alignment pin from the grommet underneath the cover.
Here I've removed the belt cover and placed it upside down to illustrate the bolt, nut, and alignment pin arrangements
Removing the alternator / power steering belt
The alternator belt is the outer belt and must be removed first. Belt tension is maintained by three bolts.
Begin by loosening (do not remove) the 12mm alternator swivel bolt
Next loosen (do not remove) the 12mm lock-down bolt.
Finally loosen the 12mm belt tension bolt. As you do so, you'll notice the belt now getting looser - keep going until you can work the belt off the alternator pulley and remove.
This image illustrates the bolt travel needed to remove the alternator belt
Remove the A/C Belt
Once the alternator belt has been removed, we can now remove the A/C belt. Begin by loosening (do not remove) the 12mm idler wheel tension lock-down bolt, labeled on the lower right side of this image.
Then loosen the 12mm belt tension adjustment bolt until the belt can be removed from the A/C pulley.
Install the new belts
Install the new belts and adjust the bolts in reverse order. The image illustrates the part numbers I used from O'Reilly's Auto - your part numbers may differ.
Tighten the tension adjustment bolts until there's only about 1/4" play at the center span of each belt with moderate finger tension. Once you're satisfied with the belt tension, tighten each of the lock-down bolts (a bit of caution here - excessive belt tension may wear pulley bearings prematurely - observe the 1/4" of center span play guide).
Before re-installing the belt and air intake covers, start the car and look for any issues with the new belts (keeping fingers well away from the new belts). Turn on your A/C to test that belt. If no squeaking or excessive belt play is observed then shut off the motor and re-install the belt and air intake covers.
Look around the engine compartment for any remaining tools, drop the hood and enjoy the ride.