C5 2010 1,6 THP aut. deceleration noise

[mf.lorant]

I am quite happy.
Tonight I have realized that when pushing the gas pedal and I rev up to approx 4000 revs and I release the pedal quickly the noise/sound appears.
With these new infos does anyone have new ideas?

[xantia_v6]

That would correspond with the normal sound made by the turbo dump valve. If it has recently got louder I would suggest that there is a disconnected or damaged hose somewhere between the air intake and the low pressure side of the turbo (where the dump valve expels the pressure).

[mf.lorant]

I will check the hoses and I am really looking forward finally finding the noise...
I will look around the dump valve first. I will later inform you about my experiences
Thank you for the assistance!

[mf.lorant]

Dears,

Some news appeared, I hope.
I/we have maybe found some clue regarding the noise.
This valve can be the failing one (please see atachment)
Do you think if I am going to change it effects the gearbox oil? I mean should I change it, or will I lose some of if I remove this piece?

Regards

[xantia_v6]

I am not familiar with that part. What is it called and where is it located?

[mf.lorant]

This is it:
https://m.autodoc.co.uk/vemo/7656727

[GiveMeABreak]

I think he means this - called a 'snifting valve' Mike. Item 3.

[xantia_v6]

The part on autofocus looks like a solenoid internal to the gearbox. The part that Marc shows above looks like a breather pipe external to the gearbox.

I don't really see how either can cause the noise as described.

I would suggest that you drive the car with your mechanic in the passenger seat and demonstrate the noise to him. Otherwise you might replace more parts needlessly.

[mf.lorant]

Thank you, I will check with him together.

Regards

The part on autofocus looks like a solenoid internal to the gearbox. The part that Marc shows above looks like a breather pipe external to the gearbox.

I don't really see how either can cause the noise as described.

I would suggest that you drive the car with your mechanic in the passenger seat and demonstrate the noise to him. Otherwise you might replace more parts needlessly.

[mf.lorant]

Hi,

I have checked it with the mechanic, he said that he cannot hear any noise coming from the lower front left of the car.
Maybe I am paranoid or I have very good hearing to hear such sounds, but I still hear it.
Now I am confused and clueless...

[GiveMeABreak]

I couldn't hear anything but the road noise I'm afraid and it was a little too quick (but then we don't want you hanging out the door with a video camera!).

Have you connected it up to Diagbox to see if there are any faults logged. There may be some intermittent faults that are not serious enough to flag the engine management warning. If there is nothing there, I would leave it. If there is a fault it will likely develop and then may be more noticeable in the future.

[mf.lorant]

Hí

I will check with that again on a ride to have live data, maybe it will give me something.

Thanks Marc!

[mf.lorant]

Hey all

Back again.
Do you know what the following item is for?


One more and hopefully last question. Can it be that the noise regarding deceleration comes from the exhaust down pipes?

Regards

[xantia_v6]

That item is the boost control valve, which is located behind the engine. If it is faulty, your will get fault codes for over-boost or under-boost.

I still believe that the noise that you are hearing is the normal operation of the turbo dump valve. It may be that something has changed on your car to make the noise louder, but the operation of the dump valve when decelerating would be normal.

[mf.lorant]

I think this is the verdict.
My car is behaving normal then.

Thank you for all the assistance and help you provided.

Regards,

Ps. If something appears in the future I know where to ask