Thread: TD6 Turbo VNT clean

Hi Guys

A little story to share that may help another. Car is a 2004 TD6 with 198km.

I have been experiencing uneven or inconsistent boost pressure for a while and it was getting the better of me. The symptoms were a very loud turbo whistle in lower RPM (sub1800) under partial throttle, then the whistle nearly instantly drops off with a noticeable increase in power @ 1850/1900rpm.

With diagnostic gear, the boost pressure reported by the engine ECU shows very high pressure when the whistle is loud, dropping of to what I would consider more normal when it quietens down. So I'm puzzled at why it is sluggish when the whistle is loud - too lean??

I have always had the opinion that either the turbo was had it or the VNT was the cause (the vanes out of position). To date I had completed the following.
* replace all vacuum lines.
* test vacuum level with gauge - OK
* test the vacuum actuator with a vacuum pump and gauge - OK
* test the control valve - seems OK but not 100%
* remove turbo for closer inspection - both sides look good, shaft has no linear movement, housings show no sign of touching, VNT actuator moves and seems to me to be OK without the sticking or gritting reported in "how to" videos out there.

By now I'm wanting to check the boost request from the ECU while driving, and maybe revisiting the control valve and swapping it out - I read it is the same as the EGR control valve and can be interchanged!!

However I remember reading about cleaning the VNT and how much of a difference it makes on the VAG cars, they are usually doing this to resolve a seized or rough moving VNT (causing overboost and limp home)- and mine seemed ok when compared to the clips I'd watched, BUT there was a growing crowd of VAG owner reporting a big improvement after a clean on a car without obvious symptoms. So with seemingly nothing to loose, I dropped the turbo off again (lucky it only takes 20minutes to remove). Removed the hot side housing and got to work - really messy, gloves required work. Put it back together and WOW - what seemed like a smooth VNT operation was now smooth and much lighter and easier to operate. Things are looking good, I'm smiling...

Back on the car, it is a changed vehicle - what I image a new turbo would feel like. Boost levels are more consistent across the range, its quiet and pulls much better down low. Cleaning the VNT ring made a huge difference...


Pretty much followed this
[ame="https://www.youtube.com/watch?v=NB0K8dnnwb4"]The messy method[/ame]

Now, the VAG crew have come up with a cheat, which is being used by a lot of people, especially as the dealers are just charging customers for a new turbo when it really only needs to be cleaned. Reading uncovers a lot of plp doing this and several plp who have tested the solution on different materials and parts and no one is reporting any adverse affects - the first report of this method I found is dated early 2008.
[ame="https://www.youtube.com/watch?v=PbUAfzi5BdM"]VW VNT clean[/ame]

It sure is interesting, and I was actually horrified when I first saw it - worth noting is the EGR plate he uses comes vertically out of the manifold directly above the turbo, very different to our manifold - What makes it more interesting is the product below and its instructions - guess what is in that can of "diesel turbo cleaner".

How to use Diesel Turbo Cleaner

Given how easy it is to remove the 2 dump pipe nuts, it would be a 5 minute job to pump cleaner into the turbo from underneath. Looks like I could have saved some time and mess

I will try this having a similar problem with daughters L322 no sign of oil or exhaust leaks .high pitched noise in lower gears under acceleration. How to you drop the turbo in 20 mins .