My 2008 2.5T S60 has developed a humming noise as I accelerate between 2000 and 2500 RPM. It does it in each gear until I reach cruising speed. Each time that the RPM drops below 2000 as the gears change, the noise stops. Each time that the RPM exceeds 2000 under a load (when climbing a hill, for example), I hear the noise again.

The car seems to run and perform fine other than that. The noise seemed to have started after having the serpentine belt and alternator replaced. The shop checked the belt and everything is operating properly. I have also replaced the timing belt and tensioner during routing maintenance recently and unrelated to this issue.

 

Any vibration or just a noise? Did they also replace the tensioners and idler pulleys? Does it make the same noise when you rev the car up to 2000-2500rpms in park or neutral?

 

Good questions. No vibration at all. Just this strange humming or whining noise that isn't very loud, actually. If I'm playing the radio, for example, it's hard to hear it. First the alternator and serpentine belt went out and I had them replaced. Then the noise started. Then the timing belt and tensioners were replaced as part of routine maintenance. The idler pulleys have not been replaced.

I don't want to mislead you with this last answer. In park or neutral it does make the same noise, but it doesn't seem to be quite as loud if that makes any sense. I also notice that if I rev the engine above 2500 RPM in park or neutral, the noise goes away.

Thanks for your help!

 

Someone responded on another thread where the symptom appears to be the same as mine that it sounds like the turbo spool. Is that an expensive repair?

 

Hearing the turbo isn't a bad thing at all. It's hard to say how expensive a repair can be without knowing what needs to be done, if anything needs to be done at all.

 

Thanks. I understand, but this is a new noise. I had never heard it before until it started about 3 months ago. I'm assuming something is wrong.

 

I would see about getting it checked out, it’s hard to diagnose a sound like that over a forum post.