My moms car, a 2002 Subaru Outback L.L Bean edition, which has the 3.0 liter H6 engine, has had a slight squeal to it for a while. Recently, it had become louder, and she said it sounded as if it were coming from more than one source. I had personally heard the squeal before, but it was never as loud as it now was. I popped the hood, and with the car running I put my ear near the alternator to try to pinpoint the location of the sound. I traced it to the serpentine belt idler pulley. I removed the belt, and spun the pulley by hand, and it was quite clear that the bearing was shot, as it felt full of grit. I replaced that pulley yesterday, but because the factory pulley was unavailable, I had to use an aftermarket part that was 2mm larger in diameter. I was worried that this would put too much strain on the tensioner because the belt was very difficult to reinstall, and that suspicion was confirmed when the extra strain caused the tensioner pulley to emit a similar sound to the worn out idler pulley. It was late, and all of the part stores were closed. I figured another day of driving wouldn't hurt, since I was going to replace the other pulley anyway.
Today, I replaced the second pulley, but this time with a 76mm unit to take some of the pressure off of the belt and bearings. Now the belt squeal was completely gone. But another squeal was heard....
This was the sound that I was familiar with, having driven the car 6 months prior when the sound had originally started. I once again put my ear near the alternator to have a listen. This time it definitely wasn't coming from the front of the engine, which had me quite worried. I checked the transmission fluid level, which was right where it should be, and the fluid looked brand new. I knew the sound had to be coming from the transmission, so I went ahead and added 6 ounces of Auto-RX to the fluid. I started the car and let it idle for a few minutes. The squeal actually became intermittent while I was standing there listening. I backed the car out of the garage and took it for a short 2 mile drive, and to my surprise the squeal at idle was completely gone, yet when I revved the engine it was still there at higher RPM. I continued driving to get the transmission nice and warm; driving a total of 14 miles before pulling back into her garage. When I returned to the house I revved the engine several times, and the squeal was GONE! I asked her to come out and listen for herself, and she was completely amazed. She had lived with the sound for months thinking it was just the serpentine belt, even taking it to the dealer, who could not find the source of the problem.
If we had taken it back for this squeal again it probably would have cost thousands of dollars for them to drop the transmission, and they probably would have replaced parts at random to find the cause, or would have replaced a bunch of parts at one time.
I will report back as to whether the sound is still gone once more miles have been put on the car.
