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Discussion Starter · #1 · (Edited)

I think it's turbo related, but I'm not confident at all.

  • It's audible on cold start (when the car is idling at 2000RPM)
  • Once the idle RPMs drop, the noise goes away.
  • The noise does not come back if I rev the car in park.
  • The noise does come back when driving and accelerating at 2000RPM
  • When I accelerate beyond ~2500 RPM, the noise abruptly stops

I'm gonna try and pinpoint the noise using a stethoscope. It seems to be coming from the driver/rear side of the engine.

I'm also thinking of pulling out the turbo and checking if the shaft is loose. Anything else I should check before I do that? Am I even on the right track?

Cheers!
 

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Discussion Starter · #5 · (Edited)
I suspected belts/steering pump/aternator initially! But the sounds is really coming from the other side of the engine, not the belt/pulley area.

When driving, the noise stops abruptly when I go over 2300 RPM. Just when the noise stops, I hear the turbo go "whoooosh" and the car takes off as you would expect. It's almost as if the noise stops as soon as the wastegate opens (or shuts? I'm not sure).
 

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Discussion Starter · #6 ·
Just got a stethoscope. Now I'm pretty sure it's the turbo :(. It sounds the loudest when I touch the turbo housing.
 

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Mark the inner to the outer parts of the crankshaft pulley. Recheck the next day and see if they are in alignment. Slipping harmonic balancers can cause belt like noise after belt has been changed. It also will not go away if silicone lube or other spray stuff is tried in attempt to quiet the belt.
 

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One Possibility is a clogged or broken catalytic converter causing backpressure in the turbo. And or wierd exhaust leak. Its so odd that thats what came to mind. Then you said it takes off normally, something may be restricting it.
 

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Discussion Starter · #9 ·
One Possibility is a clogged or broken catalytic converter causing backpressure in the turbo. And or wierd exhaust leak. Its so odd that thats what came to mind. Then you said it takes off normally, something may be restricting it.
Thanks for the suggestions! I'm gonna get under the car, check all the seals, and test the backpressure. Here is an updated video. The noise has gotten worse. It has a tinny/rattly/metallic note to it now. I'm pointing at the wastegate actuator because that's where the noise was loudest using a stethoscope.

 

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That's so weird!
I wonder if you get it stationary on a dyno or something if the noise is really still there when it is spooling up and under load.
 

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Discussion Starter · #11 · (Edited)
If I rev the car in park/neutral, no unusual noise. If I rev it up in drive, while holding the brake pedal, the noise is heard at 2000RPM while stationary.

So yeah the engine really needs to be under load for the noise to happen. I guess on cold start the engine puts itself under load to try and warm up faster, thus the noise. If I start the car with a warm engine the noise is minimal to none (until I start driving, or rev it up in drive with the brake pressed down...).
 

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I have a similar sound. When I started my car after it has been sitting for a bit. When it hits about 1800rpm the noise is there for about 3-5 seconds. Once the idle drops it is normal. It sounds like something is loose. I turned the car off immediately to listen and I could hear what sounds to be the turbo spinning down. I don’t get any noise after the 3-5 seconds. Maybe it is the turbo.


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I just wonder if it's an air leak somewhere, that can produce all manner of odd noises depending on whether its under vacuum or boost.
I'm basing that entirely on the sound of a You Tube clip, so I could be waaay off, if it IS an air leak then it won't be anything unique to a Volvo so in theory a good mechanic might have some good ideas where to start
 

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Discussion Starter · #14 · (Edited)
But if it's an air leak would it be noticeable on the stethoscope?

When I probe the stethoscope on the engine block or transmission, I hear a normal humming sound. When I probe the turbocharger housing, the noise is so loud it hurt my ears! :eek:

I'm getting it on a lift on sunday. Gonna try some of the suggestions here, and check the turbo for shaft play. Hopefully report back with some answers.
 

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I'm thinking the turbo now. Sounds like the bearings, or oil starvation.
 

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Discussion Starter · #16 ·
The noise is gone! It was the turbo after all. I replaced it yesterday with a used one from ebay.

Turbo replacement was an adventure. Every muscle in my body hurts. My neck hurts from looking up from under the car. Lots of stuff I wish I knew before I started. I'll make a write-up on it soon.

Look at that shaft play on the new vs old unit:


Here is a happy cold start:

 
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