C5 2010 1,6 THP aut. deceleration noise

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mf.lorant
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C5 2010 1,6 THP aut. deceleration noise

Post by mf.lorant »

Dears,

Hope you can assist me. As it is stated in the subject I have a 2010 C5 1,6 THP 155 aut.
When I am decelerating from let's say 60 kmh a strange like "blowing" sound comes from the engine. I can only hear it if the windows are down, from inside there is no noise. This sound/noise blowing-rattling sound and it is not the chain tensioner etc because it has been recently changed.
Any ideas what this sound/noise can be, anyone had same issues?
Thank you in advance
Regards,
Lorant
Last edited by mf.lorant on 29 Oct 2019, 19:22, edited 1 time in total.
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by xantia_v6 »

How long does the noise last?
Does it stop if you gently accelerate?
Does it sound more like an air leak or a whistle or a rattle?

My first guess is that it is a rattling heat shield on the turbo or exhaust.
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by mf.lorant »

Hi,

I can hear the sound when I'm decelerating from let's say 70-50kmh and the noise stops when the rev is lower. The noise is like an air leak sound, not rattling noise.
Do you happen to have a pic of the heat shields? Where should these rattling?

Thx
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by xantia_v6 »

The heat shields around the turbo are immediately visible when you open the bonnet. There are also heat shields above the exhaust behind the engine, on our 308, one of these resonates a little, but only when the engine is cold.

I don't suppose you are noticing the sound to the turbo dump valve? You will hear this as a whooshing sound if you quickly release the accelerator. You can hear it with the car stationary if you have the car in gear with the brakes firmly applied then press the accelerator well down for a second and quickly release it.

The dump valve is much louder if any of the turbo air intake pipes or the crankcase breather pipe are disconnected.
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by mf.lorant »

It is not the heat shields. I did a few testing and those are noiseless. It is an air sound appearing when you decelerate between 70-50 kmh. I just saw that I am repeating myself... :-D
I think it wouldn't be me who is going to solve this, I take it to a mechanic. But still, ideas are highly appreciated 😉
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by mf.lorant »

20180902_213443.jpg
I have attached a picture of the valve, is this the so called dump valve?
Last edited by mf.lorant on 02 Sep 2018, 22:26, edited 3 times in total.
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by xantia_v6 »

Yes I think that is the dump valve, it opens a passage allowing air from the high pressure side of the turbo back to the inlet of the turbo. Its purpose is to stop the pressure at the turbo outlet getting too high when the throttle is suddenly closed (as happens during gear change with manual transmission). Without the dump valve, the turbo could stall, causing turbo-lag when the throttle is opened again.
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by mf.lorant »

Do you know any other places where air can leak when you decelerate?
Thx
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by mf.lorant »

Hí,

I have changed the dump valve. It still has the same noise/sound.
The noise seems to come from the front lower left of the car.
Any other ideas?

Thanks, regards

Ps.: I really hope that this sound is not related to the automatic Aisin transmission...I am actually planning to go to a garage having a gearbox oil change
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by mf.lorant »

Anyone? No one 😔
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by xantia_v6 »

You need to give some more information.

You said that you would take it to a mechanic. Did you get a diagnosis?

Can you hear the noise with the vehicle stationary when giving the engine wide throttle in gear with the brakes on?
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by mf.lorant »

Hi,

I've been to the mechanic, but they did not hear the noise. They tested it in different conditions but nothing, that's what they say.

I tried with the car stationary and wide throttle in gear, but no sound.

So now I am puzzled...
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by Hell Razor5543 »

An automotive poltergeist with an audio fetish?
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mf.lorant
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by mf.lorant »

Hell Razor5543 wrote: 27 Sep 2018, 17:13 An automotive poltergeist with an audio fetish?

Maybe... :rofl2:

Is there a valve in the automatic transmission which can provide this valve sound when decelerating?
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Re: C5 2010 1,6 THP aut. deceleration noise

Post by mf.lorant »

Again, here is a video of the sound:


I really hope you can hear it, search for a valve sound
Last edited by myglaren on 29 Sep 2018, 15:15, edited 1 time in total.
Reason: YouTube tags
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