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Discussion Starter · #1 ·
Hi all,

I'm interested in hypotheses to investigate regarding a low whining noise I'm hearing on my new 2015.5 XC70 T6.

I have sensitive hearing, so I can hear this, and the infuriating power steering "wuh! wuh!" noise whenever I touch the wheel, over quiet music and road noise. I'd love to figure them both out!

The details:

  • Fixed, not high (maybe 630Hz?), frequency; doesn't vary with engine speed or road speed. I hear the turbo independently, so I don't think it's turbo-related.
  • Not entirely constant; it pulses/da-da-daahs, intermittent like morse code, like it's playing a tune (almost like cellphone interference with a speaker).
  • Volume only becomes noticeable with the engine under load, giving it some throttle -- e.g., pulling away from a light or up a hill, revs approaching or over 2000rpm -- but it's always there.
  • My brain positions the sound as roughly inside the engine compartment by the driver's side (left) wheel, but of course it could be anywhere.
  • Stops entirely if I shift into neutral while moving, even if I maintain revs at a point that was making the noise just a moment before. Back into Drive brings the noise back. Can't reproduce the noise if I stop and rev it in park, either.
  • I also noticed it today (I think while in park, but perhaps in Drive with my foot on the brake) with the engine's normal high initial idle, so it seems the car doesn't need to be moving.

Any ideas, anyone? A pulley, a pump, something else?

Mechanic's stethoscope is on its way, but I'd love some guesses.
 

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Discussion Starter · #2 ·
Update: I figured out that it must be a vacuum leak. Fixed frequency is the big clue.

I took the car in to the dealer with a list: first service, this noise, power steering noise, wind noise on driver side.

Got the car back today. New power steering pump (the old was chewing itself up). The noise was a vacuum leak: mis-installed intake piping, I think. So now I have a quiet car, with the exception of the wind noise; they were able to hear that but not fix it.
 

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Discussion Starter · #3 ·
Re the power steering: Volvo suggested doing a fluid flush and checking for shavings. The service manager was smart enough to overnight a new pump, then do the test; apparently shavings poured out, so it was good that the new pump arrived the next day!

Feel pretty good that the service guys agreed that something didn't sound quite right, compared to two other new cars to make sure, and didn't just blow me off — that would have led to a failure down the line, and I'd have been mighty pissed.
 

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Aaaand the next day both noises are back. Of course.
How many miles were you able to drive with the problem "fixed" before it came back?

You're lucky to have such a good dealer...
 

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Discussion Starter · #6 ·
About 100, I think. The fluid color looks the same as when I took it in, so it seems CHF-202 picks up a little color fast… or this new pump is in trouble, too.
 
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