I suspect it's a blown turbo charger .....new turbo and you should be fine... From what I know this has occurred to others...with the mileage you have

 

I'd actually love for you to be right but Turbo was replaced only three years ago. At best there could be an issue with the electronic control but the CHRA is good, blowing no smoke and the vane control ring rotates smoothly. This exhaust leak is really complicating issues and I'm looking at broadening my investigations to check the sensors even though the leak appears on the surface to be a contributor.
Dropped into limp mode again at sea level yesterday so I'm using sport mode which keeps the boost down. Amazing and it does look like the trip home is going to be a real slow slog.

 

Sorry didn't pickup that turbo had been replaced already. Was that a new original VW turbo put in?
If it's not the turbo then it's the plumbing(all hoses and connections) and sensors that come to mind

 

I don't think I've mentioned the replacement, certainly the obvious thought at this mileage. Yes an OEM by VW. I'd come to the basic conclusion about gaskets, sensors and the like but being as inaccessible as it is and not having my inspection camera, I was hoping for a revalation. The fact that the exhaust leak sound only is audible when the car is in normal mode and disappears when in limp mode is what is puzzling me. A standard constant leak would be welcome, at least I would know what I was faced with. Running the car off load with the heat shield removed shows absolutely no trace of a leak either visually or audiably.

 

Limp mode, reduced power and load on every component inc engine turbo etc etc, makes sense for it not to occur then...
You clearly have an exhaust side leak in the turbo so checking the plumbing right from the manifold to turbo and through makes sense... Don't know how much of this can be done without serious dismantling....

 

Yes, interesting situation. Absolutely no sound of an exhaust leak at idle, heat shield removed, etc etc. Understand no load, low exhaust volume and so on. I checked all the measuring blocks without load and no obvious discrepancies. Clearly it would be ideal to have the measuring blocks being recorded when the fault pops up and limp mode is engaged. I plan to drive the 1200 Km home in a few days and then get stuck in when I have ramps, extensive tools and the works. Who knows what I will discoverbut at this time it seems like the only option.

It would be nice to just discover an exhaust leak but my gut feeling is that it could be more complex, not necessarily more difficult.

 

Log your requested boost vs actual. Your leak only develops at higher load, which would also be impacted by higher elevations since the turbo would need to work harder up there vs sea level. I'd look for boost leaks first and foremost, even though you hear "exhaust leaks" and see soot evidence suggesting an exhaust leak. I would also try performing boost\pressure output tests with the engine running if the controller allows you... this might give you an opportunity to see the leak if the system is able to produce enough boost under idle condition. Use a telescopic mirror to place around the turbo if that's where you think it might be leaky.... it should fog up instantly if hot exhaust is released on it.

 

Brilliant input. I've been a bit blinded by the exhaust leak sound, and the sign of an occasional whiff of exhaust smell and smoke and must say that I have been swayed by that. Makes all the sense in the world to go chasing a boost leak, having the same symptoms. Very little chance of doing anything significant 1200 Km away from home other than a good visual inspection. Certainly there is no visual exhaust leaks when not under load. Will check tomorrow and let you know if I do see anything of interest.

 

Most boost leaks only happen once sufficient pressure is built up and the split hose\coupler\pipe can "open up"..... check intercooler end tanks if you can get to them if you can't see anything else....

 

Boost leaks or turbocharger. The turbo's in these go rather frequently in America due to the emissions crap, unsure of your part of the world though.

 

Most boost leaks only happen once sufficient pressure is built up and the split hose\coupler\pipe can "open up"..... check intercooler end tanks if you can get to them if you can't see anything else....

Good info. Constrained by location atm but will check what can be accessed before setting off and do the strip down once I get home.

 

As of 17 Aug, stuck about 300 Km from home with a serious water leak. One thing begets another. It looks like the 7P 3.0 Diesel using up or losing coolant thread. Same location and symptoms. I had already noted this as likely before this thread popped up and gained my undivided interest.

Anyway great reading this morning and car goes on a carrier to get it home and we crank up the hire broom and follow. Looks like I'll be Touareg-less for a few weeks while I assemble parts and get it stripped.

The partial drive home confirmed in my mind that it is indeed an exhaust leak, not a boost leak in the intake. While struggling up hills in limp when the car dropped down a gear to around 2500 RPM the leak noise just vanished immediately so I'm obviously vested in the outcome.

 

Well, safely home and after going down a few non car rabbit holes, the car has been delivered to me by the carrier. Despite the potential to have to strip the top of the V to find the water leak, I was kissed by the fairies and a (as yet unidentified) hose right on top was found to have a hole in it. Part number 059 121 086F. I'll now go and get that identified and hopefully get a spare part easily.

Neat little hole blown in the plastic pipe. Hard to see without a little bit of smoke testing to indicate the location.

 

No picture????

 

Wow nice find

 

Just like winning the lottery, could have been so much worse. While the local dealer doesn't have stock, apparently it's available, so soon to get this part of the defect list resolved!!!

 

Looks like this has been neglected with the raft of other things in life happening around me. Got the replacement pipe no problems, installed, a breeze, and then found my workshop aircompressor control valve diaphragm had ruptured. Took a little while to get a replacement and then I could refill the coolant using the vacuum filler. All done and no leaks internally or externally, changed the oil and filter and now just to positively locate the exhaust leak and it's all done. The urgency has gone as in the midst of all this I picked up a Cayenne with all the options that my Touareg had so I'm future proofed.