Audi A6 2.5tdi 2003 Allroad loss of power

[Oldfart]

Hi

Thanks for the information but it was a little technical for me!!! What is an N75 and how can I check if the acutator rod was is moving - how can I see it.

[bartboy]

Hi,
Posted on this thread earlier.
My cars fault has now been narrowed down to one of two faults, boost pressure sensor, very cheap or turbo vanes sticking, very expensive.
Yesterday we checked the n75 valve and it was working fine, not surprising as it's new but audi say they rarely go wrong!. The N75 valve regulates the pressure (or vacuum to be more precise) going the the actuator for the turbo variable pitch blades. If the photo's I've added have worked you should be able to see the actuator rod on the first photo. Once you have removed the engine cover it's at the back of the engine bay sitting on top of the turbo with the black (plastic braided coating)pipe going to it. Beneath the actuator which is the cylindrical thing, like a small barrel, the hose goes onto is the actuator rod. in this case it has yellow paint on it. By removing the vacuum hose and attaching a hand pump (vacuum and pressure guage) in the vacuum mode you can increase the vacuum on the actuator and see whether the rod moves. Total movement should be about 15mm. You should also be able to see the rod move if you get someone to blip the throttle to about 3500rpm when the pipe is connected. By placing a vacuum guage on the pipe which you remove from the actuator and blipping the throttel you can check if the n75 valve is working as you will see a variation in the vacuum reading as the throttle is blipped. You can trace the vacuum pipe from the actuator back to the n75 valve which is on the rear bulkhead (left hand side as you look from the front) next to the fuel filter. There are two similar looking valves together which are joined by pipes. The N75 is the one on the right and has a whit bottom as hopefully shown in the photo. If your turbo is sticking apparently there are chemicals available which can be put into the turbo (after dropping exhaust pipe) which clean it out and can fix it although not usually permanently. Turbo vane tend to stick on cars which are prdominantly used around town and never revved hard. Like mine!!!
p.s. if you don't have a proper vacuum/pressure pump you could try using a large syringe to induce a vacuum on the turbo actuator.
Hope this helps.

postscript, Yep. as feared turbo vanes sticking and turbo had to be renewed, goes great now, better gearchanges and mpg, expensive though

https://www.vwaudiforum.co.uk/forum/a...1&d=1267538514

https://www.vwaudiforum.co.uk/forum/a...1&d=1267538565

[Oldfart]

Thanks very much for the detailed instruction. I'll take a look over the weekend with your instructions in one hand and a torch in the other.


Regards

Alan