Howling sound with loss of acceleration?

Tiny
LARRY9ER
  • MEMBER
  • 2014 MERCEDES BENZ CLA250
  • AUTOMATIC
  • 128,000 MILES
No check engine on, light howling sound when taking off from at a stop. Car doesn't have initial powerful go! Car goes to all speeds and moves from gears smoothly. When the car is in park, the car revs up normal. Was told may need to replace drive belt tensioner. Other than that, I can't figure it out. I have a machine, and no codes are on it.
Thursday, April 3rd, 2025 AT 2:22 PM

5 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,615 POSTS
It sounds like the turbo can be going out but can you please shoot a quick video with your phone so I can hear the noise? That way I can tell for sure what's going on. You can upload it here with your response. It also could be a catalytic converter that has come apart or is partially clogged which can make a howling noise.
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Friday, April 4th, 2025 AT 11:06 AM
Tiny
LARRY JOHNSON4
  • MEMBER
  • 4 POSTS
This is the best I can do. It's not very loud outside of the car. And the camera barely picks it up when recording inside car. No smoke, no burning smells or any smells, no check engine, nothing leaking. The engine is not getting hot.
Video (Click to make bigger)
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Saturday, April 5th, 2025 AT 6:20 AM
Tiny
KEN L
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  • 51,615 POSTS
Can you tell where the noise is coming from, front, rear, engine or transmission? Is the noise louder when you open the hood, will it make the noise when you are not moving, also do you have any warning light on? Sorry I could not tell much by the video.
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Saturday, April 5th, 2025 AT 11:44 AM
Tiny
LARRY JOHNSON4
  • MEMBER
  • 4 POSTS
Noise is only when in drive and when I first start to go from a stop. It doesn't do for park or anything. I can rev in park and it is fine, no restrictions and no noise. Comes from the engine. Still no check engine light, no burning, no smells. Again it is only when I first begin to drive from a stop whether it be at a light or whatnot. Yesterday I put my code reader on it and it came up with this which I know has something to do with turbo. I'm just hoping it is something small like a clog or it stuck.
P0299 pd 01/01
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Sunday, April 6th, 2025 AT 5:38 AM
Tiny
KEN L
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  • 51,615 POSTS
Yep, the problem is the Turbo, sorry

P0299 � Turbocharger/Supercharger "A" Under boost Condition

So, I would remove the intake or exhaust side of the turbo and check the endplay to confirm. This guide can help:

https://www.2carpros.com/articles/how-turbo-chargers-work

Please go over this guide and get back to us.
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Sunday, April 6th, 2025 AT 1:11 PM

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