Hey everyone. My XC90 has been making a strange whining noise coming from the serpentine belt are of the engine. To me the noise sounds like a struggling power steering pump but the steering is unaffected and the fluid level is good. Using the old screwdriver to the ear stethoscope is tough because the noise seems to permeate through a lot of stuff around the serpentine belt area. I'm thinking it's either the power steering pump, idler pulley, alternator pulley or AC pulley.

The noise is definitely linked to engine speed. As RPMs increase the sound increases. When I turn the wheel side to side the noise is unaffected which makes me wonder if it's something besides the power steering pump. In my experience putting strain on a tired pump makes it whine worse.

I've included a link to an audio file. In the file I'm revving up the car a few times to about 2500-3000 RPM. This is taken from the inside of the vehicle...yeah, it's pretty loud.

It's a 2005 2.5t FWD with, *gulp* 275K miles.

Audio clip of the noise

 

you should be able to take the top belt cover off, (with out doing the whole of the plastic cover) and verify that the belt is not rubbing on the cover?

 

Yep, I'd pop off the timing belt cover and fully inspect the serpentine belt. When was the timing belt last done? last thing you want is the serpentine belt to snap and wack the timing belt in the process... Doesn't sound like an idler to me but the best way to test those is to removing the serpentine belt and feel by hand. Alternatively you can try a few simple tests:

Does it change sound when you engage/disengage the AC? That'll put a load on the serpentine belt and would probably change the tone of a noisy idler as well.

Does it change sound when you turn the steering wheel (loading up the PS pump)? If you've not serviced the PS fluid, a quick fix would be to turkey baster out as much of the oil fluid and refill, then turn lock to lock a few times and repeat. Use only the PS fluid recommended in the manual (probably Pentosin CHF not Dex ATF)

 

Timing was done at 200K so about 75K miles ago.

Turning on the AC and turning the wheel doesn't seem to change the noise at all. However the screwdriver to the ear method on the power steering pump is very noisy. Alternator is less noisy.

I'm not sure how to get the screwdriver on the tensioner without driving it into my ear canal if I slip.

I need to get the belt off and check things out but time is not on my side lately. I was hoping someone heard the noise and new exactly what it was type of a thing.


*** SLIGHT UPDATE ***
Just found a used power steering pump for $50. Going to try that and see how it goes. Gut tells me that's the issue. We'll see, gut has been wrong before, lol. Will update after I replace.

 

*** UPDATE ***

Well, it's not the pump. Swapped it out and the sound is still there, no different.


Looks like I need to change the alternator pulley. Pretty excited about this since I get to remove the power steering pump AGAIN. Probably just going to replace the whole alternator while I'm in there. Will post another update when I get that done. Until then you'll be able to hear me coming, lol.

 

I have a similar sound only during acceleration is that how yours started at first?

 

Pretty much, yeah.
Now it's loud during acceleration and idle.

 

*** UPDATE ***

It was the alternator. Replaced it and we're back to normal. No more weird looks in parking lots. Well, at least not for that reason.

Here is a quick DIY of the process.