can someone explain please

[avants2turbo]

right, here the thing, i would like someone to explain to me how/why the boost system works as it does, i understand how everything works from the MAF through the turbo - intercooler - xmember - silicon pipe - metal pipe - throttle body elbow - throttle body

I know theres an outlet to the wgfv and an outlet to the recirc valve and another to the cam cover breather in the pipe between the maf and turbo inlet and i understand why they are there apart from the breather to the cam cover, or is this a breather back into the inlet?

I think my main question is, how or where can the boost escape in or around the breather system?

I did a boost leak test earlier using the Andy P test kit, i used the 3 bungs, the one with the valve at the pipe the maf is usually plugged into, the other large plastic bung at the pipe that plugs into the metal boost pipe, and the metal one plugged into the turbo inlet hose where the cam cover breather plugs in. I compressed the system to 1.5 bar and heard a girgling noise like bubbling fluid of some sort!? Any ideas? Have i done something wrong?

When everything is restored, if there was no leak between maf- bung at the metal pipe, where could there be a leak? How would the breather system be seeing boost pressure?

Sorry for the babbling on, any help appreciated

[AndyP]

If you got it up to 1.5bar and all you heard was a steady gurgleing, then I'd say that part of the system is fine. The noise you heard is generally thought to be air passing the turbo oil seals and making the oil bubble.
Have you tired taking the 3 vacuum lines off the back of the inlet manifold and putting pressure down them and listening for leaks?

[avants2turbo]

pressure down the 3 vac lines, with what? Where do the 3 lines go? Ecu, air con recirc, rear diff controller?
If there is air getting into the oil in the turbo does that mean the turbo is shot?
Also if i just connect the boost test kit to the maf and not use the bungs am i going to damage anything? Am i going to pressurise the breather system?

[AndyP]

I use one of these



Set the regulator on the compresor to 1bar and press this into the vacuum line, you'll need somebody inside the car to listen for leaks.

I don't think air passing the seals means it's shot. I've tested quite a few cars that have done this and have run/boosted fine.

[newsh]

Yeah its the oil bubling in the turbo, dont forget there's usually 5 Bar of oil pressure on the other side when the engine is on boost

What I would do now is reconnect the metal boost tube and test the rest of the system up to the engine, listen for leaks around the throttle body and the ISV and the small hoses. You are pressurising the engine via the valves that are open and therefore some of the cylinders so it wont hold pressure for ever.

[UrS4boy]

For doing boost tests, I personally advocate taking the turbo out of the equation in order to eliminate the potential of damaging the turbo seals. Here is some AAN boost testing info that should have some relevance to your situation:

http://forums.audiworld.com/showthread.php?t=2173704

[S2central.net]

I 2nd that emotion... I do boost leak tests from the compressor OUTPUT to avoid the potential for oil gurgling as you cannot make the system air tight sufficiently long enough to detect other leaks - unless they are huge and easily spotted by that unmistakable 'psshhhh' noise of a split hose.

To that end I also block off the TB hose and PCV outlet into the MAF hose so the intact tract should be completely airtight.

[Jonas_R]

If there is a pontential that you can damage your turbo by pressure testing through the turbo, then perhaps this should be adviced when people sell these kits? Because all the kits being sold puts pressure through the turbo?