Hello @2007Conti ,
​​​As @1eapplebaum requested, please show us how you did this bypass, I recall myself asking questions of another member whom did this bypass, I don't remember getting clear answers as to my concerns as to the two tees on this circuit as shown in my video I posted earlier, my concerns were not only for the how someone would cap off or reroute a line, the concern is, if the vacuum line gets cut at the pump area on the drivers side, and also at the sensor area on the passenger side, then I see an issue, because, the two tees that are now bypassed, they do not have any pump/reservoir vacuum, and if not capped on the cut/bypassed line, that will have a vacuum leak at idle or non boost rpm, but on the flip side, because the tees are bypassed, they now have no vacuum from the pump reservoir circuit when boost is being made, so the only way that I see the bypass working is, if that the center small tee lines were in good shape, and the leak issue was with the passenger side small tee and it's lines, then the bypass would work if tee'd into this tee, but in reality, the bypass isn't necessary if the passenger side tee was the only issue, it's very important as to where this bypass ties in, as the factory tee on the passenger side is not just it's own circuit from the drivers side pump, it ties into the larger vacuum line circuit that also feeds the brake booster, the center small tee feeds the turbo solenoids at the rear of the intake, if you search some threads you will find one were the person ran the bypass over the top, and therefore supplying vacuum to the turbo solenoids I just referenced, I will have to read later if he tied into the passenger side area not only to supply vacuum to the sensor and the rear of the vehicle, but to the line that ties into the larger vacuum circuit, just as the factory setup does.

I hope that I am making sense here, I am really thinking that your issue is that you have vacuum at idle, and in the reservoir, but as you drive and build boost, the intake's one way valves close, as they should, but most likely because of the bypass path chosen, you now have no vacuum in the circuit/lines at the center of the engine for the turbo solenoids.

This is just me thinking out loud, trying to help...

Can you show us on the last picture where you cut either side ?


Purple is pump vacuum.

Green is intake manifold vacuum.

Purple to red is pump vacuum to the turbo solenoids.

Purple to teal is the pump vacuum to the large (main) vacuum circui, which also goes blue to the brake booster.

The green intake manifold vacuum also goes to the blue by way of check valves during idle, or non boost, deceleration.

The yellow goes to each turbo, and in looking at the yellow lines connection on each turbo, it is on the intake (cold) side of the turbo, and actually appears to be a vacuum source created by the turbine.





Johnny

 

Yes , I'll get photos of what I did. The thing is, it drove perfectly for 5 months after the bypass, then one day my wife came home and said that there was no power.

 

Ok, here's how my lines go out from the air tank. Please forgive the ghetto look of the lines.


From the tank. No check valve that I can see


Line follows inner wheelwell to a tee. Tee goes to front of car (not sure where)and down to the cross member



comes up from cross member and usually a tee where the bottom copper line ends. That tee provides vacuum to the rear of the car (rubber hose not connected now. Used it to hook up for smoke test) as well as up to and through the pressure sensor. Out the top of the sensor and to the top copper line that goes up through the firewall area to the center of the engine.



Copper line terminates behind the engine and is connected to the plastic tee where the old line connected

 

Think about temporarily reverting back to the original set up. Granted it will involve the old vacuum leak. We need to see if this eliminates limp mode and allows proper turbo management. Currently there are unknown variables. We need to establish a baseline.

 

But I had eliminated all problems after I converted the lines. Everything was working great for 5 months and approximately 1,000 miles. Then one day, bam; Limp mode symptoms and turbocharger codes. I replaced the turbo controller on the front of the engine. Do you think it could be the other one? Code is now showing boost sensor 2. Where is that located?

 

The controller bank 1 by the alternator is new? If yes than the bank 2 is engine out...the unit is buried. Anyway doubtful that is the issue. The controllers are not vacuum managed. They see boost ​​​​​​​only.​​​​​​. Somthing else is hapening and is reporting an implausible boost issue because certain parameters are not being reported. ​​​​​​​There may be a pinched or kinked line check under and behind the motor.

 

Hello @2007Conti & @1eapplebaum ,

I understand that the vehicle ran fine for about a thousand miles, so that would lend to the bypass working properly, but I still have concerns as to what you did with the tee on the passenger side, as it feeds into the larger vacuum circuit, and or if that tee on the large circuit side was left open, that may cause issues, as the large circuit runs to each turbo.

See my edit in my post to add the yellow information.

Now, as far as the fault codes for each bank, I see that each turbo has the position sensor implausible single, and I believe that is in reference to the sensors on the turbo waste gate vacuum actuated diaphragms, did anything happen under the vehicle, can you check the wiring and connection on each side ?

Sensors.

.








Tee to large circuit.
.




Johnny

 

Didn't find any loose wires or kinked hoses in the search just now but had a thought;

Just got in car and cranked. After a minute or so the RPM dropped and idle started stumbling. Pressed throttle and nothing from vacuum pump, however when I pushed the brake the pump kicked on, the RPM came back up and the car ran smooth. So there is a correlation. Since the only "leak" I found was out of the bottom of the pump, shouldn't the check valve keep vacuum pressure from escaping back and out of the bottom? Is it possible that when the pump is on it is keeping enough pressure in the system but when it is off, the check valve allows air to come in from the bottom of the pump thus killing the vacuum pressure?

 

Johnny, from what I can tell in my setup the tee in the right wheel well takes from the vacuum tank and then splits into the rear (muffler, etc) and then goes into the sensor and then to the middle of the back of the engine.

 

Possibly, also double check the top rubber stopper (re-vacuum pump)with the vacuum line outlet. This can dislodge from the blue tank just enough and leak. Hope that's it.​​​​​​​

 

I am not talking about your bypass tee that you added in the wheel well area, I am talking about the factory tee in the vacuum circuit along the firewall rack area, that I have now shown numerous times, if you cut the vacuum line on the drivers side, and also on the passenger side at the factory tee, how did you secure/block off each end that you now have cut and left in place at the firewall, in other words, how did you seperate the small circuit from the large circuit in this area with the purple dots ?




Also, as to the check valve at the pump and 3 blue *****, your picture barely shows the copper line connection to the pump area, please show a much clearer photo with the pump ***** and associated tubing with check valve.

Johnny

 

hi - there is a lot of fight with this vacuum issues, do you know how the phaeton users deal with that? They have exactly the same challenges?

 

OK, Johnny after looking at this a dozen times, the reason I didn't know what tee you were talking about until I saw your video is because it is well hidden. Apparently I have only '"bypassed" part of the system and completely missed the part you have been asking me about. Sometimes I'm pretty dense; sorry about that.

Now I am wondering how to connect to that part that has that tee. This makes sense because I keep getting the brake booster code. Evidently I just left the line swinging in the breeze.

 

They don't have turbos, therefore they don't have these vacuum lines, that's my thoughts ofcourse.

Just like my Audi A8L W12, no turbos, never any vacuum leaks with lines, at over 200 K miles.

Johnny

 

OK, looks like I am going to remove the steering rack. That seems to be the only way to access these lines that I should have dealt with last year.

I know there are threads here dealing with the rack removal, but for those who have done it, any words of advice or tips?

Thanks.