MK5 Golf GTI

All Things Mk5 => Mk5 General Area => Topic started by: bestygti on January 05, 2015, 10:50:29 pm

Title: Strange noise when letting off throttle on boost
Post by: bestygti on January 05, 2015, 10:50:29 pm: Hi guys,

Bit of a hard one to explain but its really bugging me so I'll give it a go. I've got a ed30 with a neuspeed p flo on it, everything sounds normal when going on boost but every now and again when I let off on boost there is like a loud 'Bwoaaarrr' sound, it sounds like the induction kit is either sucking in/blowing out or resonating? Maybe like a vibration but its something definitely to do with boost. Bit worried its something to do with the turbo but it boosts fine with no strange noises!

The noise doesnt happen all the time only every now and again, its so hard to explain but it sounds like someone farting or blowing their nose hahaha but quite loud? Definitely like a resonating sound

any ideas where I can start to check would be great, recently replaced my PCV so wondering if it could be anything to do with that?

Cheers

Ian
Title: Re: Strange noise when letting off throttle on boost
Post by: muff1991 on January 06, 2015, 04:20:26 pm: maybe check your diverter valve incase its faulty when boost is being diverted??
Title: Re: Strange noise when letting off throttle on boost
Post by: bestygti on January 07, 2015, 08:08:27 am: I have a dv+ mate could this be an issue?
Title: Re: Strange noise when letting off throttle on boost
Post by: GTImike on January 07, 2015, 11:54:07 am: Its wastegate flutter from the turbo, nothing to worry about but a Neuspeed or similar highlights the noise. Its more apparent if the car has been remapped.

You can actually generate the sound of your own accord when gently accelerating (if that's your bag), let off the throttle then lightly tap the accelerator and put your foot back on the pedal, this should generate the same noise that you are hearing. I'm a 30 something father of two so its not something I do by the way!

Also, Its not advisable to keep repeating the above procedure (I believe) as it stalls the turbo mid spin to create the noise and over a long period could damage the turbo. I've got a Neuspeed on mine too and think its the most notorious for generating this sound from what I've read.
Title: Re: Strange noise when letting off throttle on boost
Post by: bestygti on January 07, 2015, 04:00:20 pm: Thanks for the reply mate but the flutter isn't the issue. It'ss when I am accelerating and I let off without tapping there is a loud drone sound, like a 'bwoaarr' or a resonant sound
Title: Re: Strange noise when letting off throttle on boost
Post by: bestygti on January 08, 2015, 12:37:09 pm: Any more ideas? Really pulling (whats left) of my hair out now ha!
Title: Re: Strange noise when letting off throttle on boost
Post by: Dan_FR on January 08, 2015, 12:43:05 pm: Video needed......
Title: Re: Strange noise when letting off throttle on boost
Post by: Johnboy2110 on January 08, 2015, 01:21:12 pm: If you still have the oem airbox, you could put that back on and see what happens then?
Title: Re: Strange noise when letting off throttle on boost
Post by: ROH ECHT on January 08, 2015, 03:57:48 pm: Video provided....

I kid...does it sound like this? :drinking:
Title: Re: Strange noise when letting off throttle on boost
Post by: bestygti on January 08, 2015, 04:37:46 pm: Thanks for all the replies, I have a video but its very difficult to hear, I will try and upload it now and then link it.

Its definitely not the turbo flutter, had that since I have put the neuspeed on and it makes me giggle like a small child whenever I do it haha.

EDIT: http://s985.photobucket.com/user/ianbest1309/media/20150105_171956.mp4.html?sort=3&o=0

That is the link to the video, the noise is as I let off at 4 seconds into the video. Doesn't happen the second time I let off so ignore that.

Not a very good representation of the sound, you have to be in the car to hear it! It's quite loud...

Any ideas massively appreciated

Ian
Title: Re: Strange noise when letting off throttle on boost
Post by: bestygti on January 08, 2015, 04:48:00 pm: Also to add, every now and again it flutters on its own when it does the noise, it has never done it before.
Title: Re: Strange noise when letting off throttle on boost
Post by: ROH ECHT on January 08, 2015, 05:30:53 pm: It doesn't sound metallic does it? More like air, yes?
And it still makes boost like before?
Title: Re: Strange noise when letting off throttle on boost
Post by: bestygti on January 08, 2015, 08:34:01 pm: Yes definitely not metallic, and definitely an 'air' sound. It sounds like the pipe for my induction kit is vibrating almost, like there is a vacuum in the tube and its leaking out of a hole releasing the pressure, a bit like a balloon being let off sound.

And yes, it makes boost exactly the same, no lights or anything.
Title: Re: Strange noise when letting off throttle on boost
Post by: ROH ECHT on January 08, 2015, 09:37:12 pm: If it is a high pitch whistling sound...I would replace the PCV.
But first, when the breather is functioning properly, the oil filler cap will be EASILY removed when running. Try removing the cap when it is running and if it feels tighter than when not running...replace the PCV and see if that fixes it.
Title: Re: Strange noise when letting off throttle on boost
Post by: bestygti on January 09, 2015, 11:13:12 am: Not a high pitched whistling sound mate its a very low pitched sound. The PCV has just been replaced within the last month.
Title: Re: Strange noise when letting off throttle on boost
Post by: ROH ECHT on January 09, 2015, 05:08:54 pm: Another noise maker is the timing belt can rub and it is a repeating sound that can go away momentarily. The other is the cam tensioner. The belt makes a dull roar sound and are mostly present at the beginning and end of giving it more throttle...when they go from slack to tension and back again. But you likely changed that belt @ 80k miles. A good sound clip vid would be a bonus. Have you gone through and inspected all of your connections from the air filter to the throttle body?