I own a 2007 Subaru Forester. I swapped both belts on the car however it still squeaks when i decelerate. Before the belts were swapped it would squeak only when I accelerate and decelerate. No issues when maintaining speed. Any ideas?
Perform the tests listed in this post to determine whether you have a tensioner, alignment or a worn belt issue
How to test for serpentine belt noise
Perform the test under the same conditions as when you hear the noise. For example, if you hear a squeal first thing in the morning on a cold engine, test it under those conditions. Since you’ll be leaning in close on a running engine, be safe and remove loose clothing and jewelry. And use a powerful flashlight to see where you’re shooting the water. Have a friend help you, especially if the noise only occurs at higher RPMS. And you really want a second person there to shut off the engine if you stick your hands where the don’t belong.
Most belt chirps and belt squeals occur in the shortest spans between two driven components. So start the engine and spray a stream of water onto the ribbed side of the belt before it wraps around a pulley.
If the noise goes away, but returns again in a few minutes, the problem is misalignment.
If the noise gets louder, the problem is too little belt tension.
To diagnose misalignment, start by using an automotive stethoscope probe. Click here to read how to do that.
If you suspect a tension issue, click here to read about testing belt tensioners.
You may need a long wrench to move the serpentine belt tensioner.