tuccatucca

Hmm the line should hold vacuum, both sets of them. There is also a little Y (or T) fitting that connects the lines from the N75 to the turbo's on either side - if you dont hold vacuum check the connections at the T fittings as well, it might be just your clamps or T fitting has cracked which I hear is pretty common. However, if you take the T fitting off and test the lines independently and 3/4 of them hold vacuum but one of them doesn't.... then that is what happened to me and the cause was this line that I had to repair, and it will leak a fairly significant amount of boost.

Good luck

tuccatucca

Actually - I ready what you said again.

If it SLOWLY leaks - how slowly?

I mean you shouldn't have any leak whatsoever - but if it is slowly leaking, depending on how much / how fast, and if it is one of these lines to the wastegate... you may choose that its not worth the work to change it. I'm not sure.

This took me realistically probably 15 hours to get at. Its pretty much the first 3 hours to lift the car remove the carrier and stuff, then the turbo pipe removal or slide forward, and motor mount, and all that... so keep that in mind. My vacuum line was a HUGE tear, torn about 1/2 way around, so it was a massive source of a leak and I had no choice but to address it.

28cmod

A tear in the WG line should cause overboost not a boost leak correct?

tuccatucca

Hmm, thats right, and that is consistent with the code I was getting but I guess technically, it creates both??

Some of the boost goes into the vacuum lines to control the wastegates to cap off the boost, so... I guess as it is leaking out it actually forces the boost to keep ramping up because the turbine wheels don't slow like they should (due to building pressure in the wastegate control lines)

That's my guess, apparently the overboost code is actually almost always due to a leak

complacentsee

Both. The boost leak is rather minimal compared to the total amount of flow.

The wastegates crack with pretty low pressure on our cars, the "boost" leak on the wastegate actuator lines basically causes one or both turbos to create maximum boost possible at all times. It is all relative to the location of the leak and size of the leak. It can destroy the turbos in a breeze.

I repaired mine by routing a hose around the engine to the bottom of the car and then to the waste gate. I replaced the damaged portion of the line upon the next engine pull. (turbo rebuild)

28cmod

The lines to the waste gate only see pressure when the ECU tells the N75 to give it pressure to open the waste gates. When the N75 is closed those lines see no pressure as a result of boost, so should not cause a boost leak.

I saw where you replaced it and the boost leak is fixed. The only thing I can figure is that when the car began to build boost the WG was opened by exhaust gas pressure because there was no resistance in the line back to the N75.

Does this sound right or am I missing something in my understanding of how the system works? I have been chasing a boost issues sense I went stage 3, only seeing 17lbs instead of the expected 21. No boost leaks found, the N75 line holds vacuum although it does sometimes VERY slowly loose it. The next thought is that my WGs are opening too soon. If I unplug my N75 I am only seeing 4.5 lbs of boost instead of the expected 6.5-7. I believe the crack pressure on the KO4s is 6.5 and KO3s are 7.5 based on what I have read.

B5in

Ughhh I need to do this

gsxeclipsepsi

By any chance can provide the steps it too to get to the waste gate line?

I wanna see if I can do it my self without too much effort.

A rat has chewed thru my wastegate line about a inch past the hard line near the T. If this is gonna be a big job and I dont wanna do it the landlord will be covering this repair.

kingofqueenz788

did u hear any tist tist noise coming from this line ? when accelerating letting off then accelerating again.

TheHud85

I have done this repair on my car as well, like others have said by dropping the sway bar and removing the motor mount and bracket. Was a monumental pain and took a while to do but it's definitely doable on the car. Rather than buying the new part from Audi, I opted to cut off the crimp fitting, then placed a section of vacuum line inside a section of fuel line, then put the heat resistant cover around that and clamped the crap out of it. Six months now and still boosting strong!