Strange duck noise on vac

[Deano Exa]

Hey guys,

I have this strange noise coming from the engine bay, after I hit boost. You can hear it after full boost, but is most prominent after just coming on Boost in low revs, then letting off the throttle. The best way to describe it is it sounds like a duck quacking. A long drowning quaaaaaaaaaaaaak. Could almost describe it as a loose bolt rattling vigorously.

I'm thinking it's a vac problem, leak, or a vac line is been constricted, actuator or stuck waste gate... Or it could also be something driveline which occurs when the car is thrusted forward after coming off the throttle?
This is going to sound weird, but you know when you get a leaf and close it in half,and then blow across it, it creates a vibration through the leaf which makes a sound... That's it! Haha.
I would post a video but I'm on the other side of the world... Trying to sleep and this issue is doing me head in.

Anyone experienced this, or have any suggestion?

Cheers guys
Deano[/quote]

[JETETT]

my fuel pressure reg made that sound on start up

[Deano Exa]

Mine does that also, like a priming noise? So don't think it's that.
Oh just to make a note, I haven't noticed any performance issues or other problems.

[JETETT]

sounds like the old ruler trick on the edge of the table flicking it down and sliding it in, i know it doesnt sound like the noise ur experiencing but just a thought

[Deano Exa]

Ok I got it.
Get a piece of a4 paper, fold it in half, then with the paper folded in two, blow between the two pieces... The vibration will make a noise. Try it, you'll know what Im talking about.

[Damo]

Hey guys,

I have this strange noise coming from the engine bay, after I hit boost. You can hear it after full boost, but is most prominent after just coming on Boost in low revs, then letting off the throttle. The best way to describe it is it sounds like a duck quacking. A long drowning quaaaaaaaaaaaaak. Could almost describe it as a loose bolt rattling vigorously.

I'm thinking it's a vac problem, leak, or a vac line is been constricted, actuator or stuck waste gate... Or it could also be something driveline which occurs when the car is thrusted forward after coming off the throttle?
This is going to sound weird, but you know when you get a leaf and close it in half,and then blow across it, it creates a vibration through the leaf which makes a sound... That's it! Haha.
I would post a video but I'm on the other side of the world... Trying to sleep and this issue is doing me head in.

Anyone experienced this, or have any suggestion?

Cheers guys
Deano

[/quote]

You have a boost leak post turbo pre throttle body. A rubber hose/joiner which is doing the vibration thing with the pressure spike in the plumbing following throttle close. Either that, or if you have a BOV I'd be checking it.


Damo

[Deano Exa]

Cool, thanks Damo... Something to start looking at. I have got a bov which I recently loosened to soften the sound. there is an exhaust leak near the waste gate also...

[Deano Exa]

This is an old post but, thought I would write in and give an update.
So, after removing the external wastegate, bov, boost controller and all the silicone elbows, I could not find a leak. Though, whilst cleaning some oil from the stainless steel section of the inter cooler piping, low and behold, a nice split in one of the ss pipes, big enough to fit a 10c piece through. Also, the o2 sensor is in close proximity to this hole. So i believe it was getting all sorts of mixed signals etc.
Getting a new piece made up today, and will reinstall tonight! Should fix the noise at least and some lag hopefully. Will post back and let you all know how it went.

Deano

[Deano Exa]

Ok, so got the piping welded up, put it all together tonight, and all I can say is wow! The car has never run this well, which tells me there was a leak for a while. There is no hunting on idle, car starts easier, throttle response is hugely different, and hitting higher and harder boost.

I know it goes without saying, but such a small boost leak made such a big difference!