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‘14 XC70 3.2 AWD, ‘17 BMW M240i
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Discussion Starter · #1 ·
Just when the weather turned cold I noticed that my car started to whistle. It's pretty high-pitched, only audible when the engine is running, and sounds like it is coming from under the dash. I have eliminated the climate control system and radio (turning them off changes nothing) and I can't hear anything if I pop the hood and listen around the running engine. It is most audible at idle, but doesn't change pitch as the engine revs up or down.

What do you think? Could it be something like a vacuum leak? (Does Volvo even use vacuum-operated motors anymore?)
 

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7 dwarfs? :rolleyes: :facepalm:
 

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‘14 XC70 3.2 AWD, ‘17 BMW M240i
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790 Posts
Discussion Starter · #3 ·
It has something to do with power steering. When I turn the wheel while stopped, the sound changes. I'll have to poke around, maybe it is coming from the rack?
 

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‘14 XC70 3.2 AWD, ‘17 BMW M240i
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790 Posts
Discussion Starter · #4 ·
It finally got warm enough that I felt like getting my hands dirty, and I think I found the problem: serpentine belt idler. When I slacken the belt and spin it by hand it has that "skateboard" sound of a dead bearing, plus there is all kinds of visible slop if I just grab the roller and move it around. The tensioner seems better but I have to imagine it isn't far behind. I just ordered a new tensioner, idler, and belt just so I don't have to wast time taking it apart twice.

For the sake of posterity the symptoms are as follows:
-High-pitched wistle that sounds like it's coming from the dash, and hard to pinpoint from within the engine bay. Just loud enough to be annoying but not frightening (yet).
-Worst on cold start, especially when ambient temps are below about 40F
-Easier to hear at idle, gets drowned out by engine and road noise once rolling.
-When idling and stopped, it goes away briefly if I turn the steering wheel a few degrees in either direction.
-Once the engine is fully warm I can't hear it over the radio and blower.
 

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‘14 XC70 3.2 AWD, ‘17 BMW M240i
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790 Posts
Discussion Starter · #5 ·
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