Hi all, I drive a 2003 MY04 Subaru Liberty 2.5i Luxury. I've noticed it makes a strange whirring sound after starting the engine. This sound increases in pitch as the engine is revved. Could this be the alternator? I have uploaded a video here. https://vid.me/SBO2

 

Thanks

Sounds like a bad bearing in the alternator. To confirm it, use a long screw driver as a stethoscope. Touch the blade tip to the alternator case, the other end, press to your ear. This should tell you if the noise is coming from the alternator. If not, apply the test elsewhere on the motor to find the source of the noise. Pretty sure it is a bad bearing making all the noise.

Okay, thank you! I'll check this in the morning. If it is the alternator, should it be replaced? Or should I simply monitor it for the time being, and do something if the sound changes?

Another way to locate sounds is to use a piece of tubing, like 3/8 or 1/2" . Sometime the tubing or the screwdriver method work better on different noises / causes.

 

Get new bearing, and replace, or get an alternator. You probably have a few days, maybe more, but why wait until you are stranded?

Okay, thank you! I'll check this in the morning. If it is the alternator, should it be replaced? Or should I simply monitor it for the time being, and do something if the sound changes?

If the bad bearing sound is coming from the alternator, you will need to replace it soon. At some point, a bad bearing will "lock up," and refuse to rotate. When that happens, if it is the alternator, it will not let the shaft spin in the alternator. The alternator belt will heat up and break, and then you have no electrical charge going to your battery. At that point, you won't be able to drive far because the battery will go dead.

Okay I just tried the screwdriver method, and it's definitely the alternator. It's a Mitsubishi A3TG00491. I'll try to get a used replacement as soon as I can. Thanks!