Sucking/gurgling noise from intake

[prj]

Aha, now I see the pic.

What I don't see is - where does it breathe through?
Is there anything connected from the catch tank back to the intake?
Is there an open port to atmosphere?

It must breathe to somewhere, otherwise you will build huge pressure in the crank case and risk blowing your turbo seals and so on.

[momento1]

its doesnt breath to atmosphere.
the upper hose you see in the pic with the brass 90degree fitting connects to the factory hardline which then returns up the back of the black into the top pipe of the valve cover which returns to the intake hose. This is where the loud sucking/gurgling noise is coming from which i can hear through the airbox...

when the bonnet is closed, the noise almost sounds like the chatter you get when you have a lightened flywheel... which in this case its not that noise, and i dont have a lightened flywheel

[prj]

Have you checked and made sure that tank is not full?

[momento1]

definitely not full...
only 1-2mm in the bottom of the tank... if that

[UrS4boy]

The pancake is not a valve, it's the so called flame trap, if you mean the black one. You don't need the OEM valve, you can just blank that portion off and only run it to the MAF-Turbo hose... .

Disagree Dmitri on 3 points:

1. What part of "pressure regulating valve" is not a valve. It isn't necessary for a valve to either be open or closed and not something in between to make it a valve. Item 3 from this ABY diagram (below)

2. The flame trap is something entirely different. Item 5 below and in the photo under the diagram.

3. If the Audi engineers put the pressure regulating valve there, they had good reasons, i.e. to help control the flow of crankcase and cam cover vapours under booth boost and non-boost conditions. IMO it should be there for a normal (non-racing) application.



Flame arrestor (aka flame deflector plate) new and old.


Photo courtesy of Jamo

[prj]

I stand corrected then. I always saw it more as a one piece solution.
I wonder what parameters that "pressure regulating valve" has, never really opened one of them.

[momento1]

well i do know that they can fail... i had to replace one on my B5 S4

[UrS4boy]

I stand corrected then. I always saw it more as a one piece solution. I wonder what parameters that "pressure regulating valve" has, never really opened one of them.

Here are couple of schematics of the pressure regulating valve from a current thread here: http://www.s2forum.com/forum/showthread.php?t=38374

There is a diaphragm, a spring and an orifice (plus inlet and out let):

[momento1]

ok so i fiddled around with the hoses last night to get a closer look....

the one way bleeder valve is functioning just fine, its not the 034 billet valve but it is definitely of good quality and flowing the correct way.. so thats not the problem. While i was back there i checked all the hoses and while there was no leaks or splits, i can see the small hoses going to the FPR from the manifold looks ratty and will definately need replacing before it fails... Glad i had a good look back there now!

i also fixed up the kinked hose going to crankcase from catch tank with an elbow fitting, but that didnt sort it either

the noise is still there.... but it definitely there only in idle and very light throttle but not on boost...
so im hoping that by fitting the pancake valve (once i receive it) it will regulate how much "sucking/gurgling" it draws from the intake...

i took a quick video last night with my iphone and would love to know how to upload it so you can hear the noise im refering to... anybody point me in the direction to upload this video?

[momento1]

Ok just thought I would update this.

So I installed the prv pancake valve and I also replaced the after market pcv back to an Oem one.

Finally it has stopped the noise. I think the old pcv was weakening and opening too easily under vacuum. I noticed that by sucking on the Oem valve it is quite hard to suck through as opposed to the old one which was easy to suck through

Now the car is holding boost great and pulls strong.
Awesome help guys also.
Thanks everyone for their input

[UrS4boy]

...Now the car is holding boost great and pulls strong.
Awesome help guys also. Thanks everyone for their input

Yay.

[VagOrBust]

@Momento1: Sorry for the tread hijack, and glad to see you've got your problem solved.

@UrS4Boy: Am I reading picture nr 2 correctly when I say that picture nr 1 is wrong in that the flow from the crankcase will always go through the pressure control valve and the flame trap, even when idling?
(Thus placing a catch can directly after the flame trap will work 100% of the time.)

[UrS4boy]

@UrS4Boy: Am I reading picture nr 2 correctly when I say that picture nr 1 is wrong in that the flow from the crankcase will always go through the pressure control valve and the flame trap, even when idling?(Thus placing a catch can directly after the flame trap will work 100% of the time.)

Yes.

[JP]

As prj said the black pancake unit is a flame trap and is not 100% necessary if running a catch tank as the catch tank will perform that job.

Breather system is a very simple principle inwords there are the following functions.

Under the intake the one way check valve performs the function of allowing crankcase pressure and carbon cannister pressure to be sucked into the intake under vacuum conditions like idle cruising and over run. Under boost this valve seals to prevent the crankcase pressurising.
If it gets stuck open bad news.
If the pipe from the block to the valve becomes blocked the engine will smoke under idle and over run conditions.

Next you have the rocker cover that goes down to the crankcase to meet up in a junction housing of which one goes to the main crankcase and the other is the afforementioned pipe that goes to the one way valve.

The main outlet if the junction box is what makes it's way back to the intake tract. This is the line the firetrap sits in or the catchtank.

To diagnose the gurgling first check the catchtank is not full.
Next disconnect the one way valve and take it out the system. Suck on it on both sides. It should only allow air to pass in one direction. The direction of flow should be from the block towards the intake.

If the firetrap is still in the system remove it and drain all the oil out of it if you wish to keep using it make sure it is the right way round this unit is directional for it to function correctly as a fire trap.

If all these things check out do a compression test to check if there is any ring/piston issues.

Hth JP