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Whirring sound from 2001 Subaru Outback engine

My girl friend’s Subaru Outback recently has developed a sort of whirring, almost whining sound that is more noticeable when idling, although it never really goes away. I have heard a similar, but worse sound from a 99 Merc Sable next door. I’m wondering how urgent dealing with the noise from the Subaru is, because I don’t want it to progress to that Sable sound.

Mileage might help narrow the field.

Noise only when idling?

Tranny in gear or not?

The Outback has ~90,000 miles. The whirring, whiny sound sound occurs whether in gear nor not, but is more noticeable when at idle, especially when it first starts up. It is harder to detect when at highway speed, but there are competing sounds then.

Just out of curiosity, is this a 4 cylinder or a 6 cylinder engine?
I ask because the 4 cylinder uses a timing belt, and if that belt has never been changed, it is now due (or overdue).

When a timing belt is changed, it is recommended that the water pump be changed. Since a bad water pump may make noises like what you describe, it is worthwhile to check her service invoices (she DOES save them, I hope) to see if the timing belt and water pump have ever been changed. If not, a snapped timing belt will cause enough damage to result in a repair bill of $2,000.-$3,000., in addition to the cost of the timing belt and the water pump.

If there is a idler pulley for the belt tension then the bearings in it may be going bad.

Have you tried to determine the source of the sound? There are several pulleys turning when the engine is running: alternator, power steering pump, AC compressor, and an idler pulley for the AC belt. Any one of these, or a loose drive belt, can make a noise such as you describe.

I agree with VDCdriver’s advice concerning the timing belt and water pump, assuming this car has the 4-cylinder engine. If the timing belt has not been replaced, your GF should make an appointment to have it done soon. There are several pulleys associated with the timing belt, and one of them could be making noise.

But the timing belt needs to be replaced regardless of the noise. If it breaks the engine will suffer significant internal damage. While this is being done all of the pulleys can be checked, and new belts should be installed.

That should eliminate the noise.

Many thanks for the advice. "It is a four cylinder, and I will for sure want to see that she doesn’t break her timing belt.

This sounds like it’s worth looking into. I hadn’t thought aboput the idler pulley. I wish they had this sound on the CT website.

Pulleys seem to be the common theme from a number of commenters here. I will definitely look into this possibility.

However, don’t forget about the timing belt and water pump!

Yes, don’t forget the timing belt and water pump.