VNT Repair Procedure

These are the bolts that hold the housings together? I just used a 10mm box end with another wrench bound in the open end for leverage. If you've already rounded them off it may be a bit tougher. Irwin extractor?

Unfortunately, I had no choice but to remove my actuator. Any hints on reinstallation and adjustment? I have an OBD cable and Vag com.

MEwan said:

Unfortunately, I had no choice but to remove my actuator. Any hints on reinstallation and adjustment? I have an OBD cable and Vag com.

Click to expand...

I had one replaced last week, we just measured the length of the rod from the actuator body to the tip with a caliper and compared it with the old actuator. Add a few 0.0X mm for when you fully tight the adjusting bolt lock.

DBW great write up. I hope I dont this soon but if i do Thanks in advance.
Rob

Please forgive my ignorance yet again. I used to be into turbochargers about 8 years ago. I had an Eagle Talon that ran 12 sec quarter miles. I also love gas turbine engines(M1 Abrams,rotorcraft). However, this VNT stuff is new to me. I am assuming from DBW's repair post that the inlet vanes are variable so that exhaust velocities entering the hot side are constant.

I suppose this is to eliminate turbo lag vs top end boost?

What actuates the vanes? Is it actuated by centrifugal force and precision balanced?


Thanks all!

Seriously... these bolts are seized. I've tried (gently) whacking them with a hammer, soaking them in WD-40 (for over a week), and various wrenches. So far the casualties are my smallest 10mm hex socket, an adjustable wrench, and a 10mm open wrench, as well as the bolt itself. Most of the other 8mm bolts are just as bad. What gives?

Fortuna Wolf said:

Seriously... these bolts are seized. I've tried (gently) whacking them with a hammer, soaking them in WD-40 (for over a week), and various wrenches. So far the casualties are my smallest 10mm hex socket, an adjustable wrench, and a 10mm open wrench, as well as the bolt itself. Most of the other 8mm bolts are just as bad. What gives?

Click to expand...

Heat it red hot then put a good quality socket/box wrench, preferably a 6 point, on it and work it off. Loosen-tighten back and forth until it feels free.

is there a way to ensure that this process is what you need before doing it my turbo is sooted closed i think and i would consider either replacement or cleaning but I would like to be 100% sure that it is the turbo heard tell of somthign in group 11 can do this but dont know what. Searched but can find anything helpful. Any idea's anyone?

there is an output test for the VNT. With the engine running, run this test and it will cycle the linkage. If it isn't going full cycle, you have to determine if the right pressre/vacuum signal is getting to the actuator, and you have to make sure that the actuator is able to use that signal and not lose it to a leak. If the actuator has no leaks and the signal is getting to the actuator, the vanes are sticking.

I think... Someone will give me the big WWF smackdown if I'm wrong.

Skymedic said:

...I suppose this is to eliminate turbo lag vs top end boost?

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It can't really eliminate turbo lag completely, but it helps some. The vanes will work to maintain back pressure in the exhaust system which helps throttle response in the low end (gasser technology here - please excuse me, guys) but doesn't help us that much wtih throttle response since diesels don't have a throttle plate.

It works by directing the exhaust directly (for high boost by accelerating the turbine) or indirectly (produces lower gas flow and higher back pressure for lower boost) into the exhaust turbine. The vanes are a method of boost control that allow a quicker spool up of the turbine at lower engine output levels as well as control of the boost pressure at any level the computer selects. Whether the VW ECU controls it to that extent is information I do not have, but it would be possible.

What actuates the vanes? Is it actuated by centrifugal force and precision balanced?
Thanks all!

Click to expand...

Rather than having a waste gate that works by opening and dumping exhaust when intake pressures get too high, the vanes are separately computer controlled. There is a vacuum actuator on the turbocharger. The vacuum supply line comes from the famous N75 solenoid. The vacuum actuator on the turbocharger body moves a rod that in turn moves the vane actuator hardware that is illustrated in DB's .pdf file.

There is allways an easier way

Very good article and pics on how to clean the vnt turbo however it is very labour intensive and techical to most backyarders

I have been using a new ultrasonic cleaning process that does the same thing in half the time and cost

I am currently looking into cleaning the intake side of the system as well
i am going to try it and let all know how it works out!

http://forums.tdiclub.com/showthread.php?t=148269



WiLdTdI

could this have ben what happened to my turbo?! (vanes sticking open)
http://forums.tdiclub.com/showthread.php?t=143880

Can't split the turbo housing.... Any ideas ?

I have fuinally got round to getting the turbo off my 2001 TDi Golf.

The turbos is on my bench and I have Drivbiwires method printed out and...... I have fallen at the first hurdle.

I can't get the casing appart. The bolts came out really easily but I just can't get the housing appart.

I have sprayed a ton of release fluid on it over the last 3 hours. An di have been hitting it repeatedly with adrift and swearing at it too.

Has anyone got and good ideas how to get it appart ?



As an aside.

I spayed a can of carb cleaner into the exhaust side of the turbo. Tons of carbon came out and the actuator lever moves really freely now with a flick of your finger. Could that have done the trick ???

No turbo boost.

Excellent data drivebywire which I suspect I may have to utilize.
My 02 1.9TDI Passat 130ps has very limited and intermittent turbo boost.
Ran fault code test;

17664 engine temp sensor
17964 turbo pressure control
17552 air flow meter.

To date I have replace both N75 valves, air mass meter, fuel filter, air filter, checked all vacuum hoses, checked intercooler for blockages, checked operation of VNT actuator, (this moves freely by hand and also when rpm is increased).

Fault occurred for the first time when climbing steep incline under 3/4 throttle, since then no real turbo boost has been available and limp mode is incurred with wide throttle settings or when under load.

Any help with this will be greatly appreciated. I am new to this site which I think is excellent.

Many thanks
tiffyh UK

I had to put the car back together ready for work today so I wasn't able to get the casing appart.

So effectively all I have done is give the exhasut side a flush with Carb Cleaner. The VNT arm is really free now.

I have not had the limp mode again.

I suspect that this is just a temporary repair. If limp mode comes back I will post again.

I managed with a torch to work one of the stuck bolts out. The others are still not budging. What's the next step? Welding bars onto the bolt heads and turning?

Ah, some creative license with a dremel to turn 10mm bolts into 8mm, and 8mm to 6 got the rest of those damned bolts out. The air compressor side came off easily and I'm cleaning the housing now. The exhaust manifold is still welded on with rust though. Any hints on how to get it off? (obviously I'll wait till I have new screws for the air compressor so I can replace it and keep it shielded).

Why not a preventive maintenance procedure - does any one do that. Say 50k or whatever.

This is really only necessary if the turbo vanes are sticking. So, why do it if they're not? They'll get soot on them in about 10 miles anyway.

whitedog said:

there is an output test for the VNT. With the engine running, run this test and it will cycle the linkage. If it isn't going full cycle, you have to determine if the right pressre/vacuum signal is getting to the actuator, and you have to make sure that the actuator is able to use that signal and not lose it to a leak. If the actuator has no leaks and the signal is getting to the actuator, the vanes are sticking.

I think... Someone will give me the big WWF smackdown if I'm wrong.

Click to expand...

Any more information on this output test?? I am getting a new 2003 Jetta, and this seems like it would be a good test to perform with the VAG-COM as soon as I get it.

the vag com is intuitive enough that you should be able to find it. If you don't want to wait do this:

get a coupler (hollow plastic tube with barbs on both ends) there is actually one or two under the hood so you could borrow them if you remember to put them back. Anyway, remove the hose going from the N75 to the turbo (labeled "OUT" on the valve) and the vacuum hose (labeled "vac") connect these two hoses together. You are now supplying full vacuum to the VNT actuator. Now, jack up the car (you may be able to do this from above, but it is impossible with a beetle) and use jack stands or some other means to properly secure the vehicle as you'll be under it. un plug the hose to the VNT. start or have the car started. Now apply the hose to the barb coming out of the actuator and watch the arm. It should travel a decent amount - around an inch. If it's hardly moving or not at all then you know.

Method number two: require a vacuum cleaner or pump. Take your electric vacuum source and adapt a length of hose that is the same size as what's on the VNT to it. Jack up the car, secure it, yada yada yada. Pull off the hose and do the same test by applying the hose with the vacuum to it and observe.

If I can figure out how to reduce the size of a movie coming out of my video camera I'll post it showing the full travel.

The movie would be great, and I'm sure when I get the car in front of me (only one more week and I go pick it up!) it'll make more sense. I'm familiar with turbo'd cars (just not diesels yet) so I can visualize what your explaining and I'll have a go at it when I get the car home

Mildly OT, but does anyone know what the metal parts in the hot section are made of? I get that the housing is iron... are the vanes and rings Inconel? How about the turbine?

ever curious,
Eddy

Well I made the video before I did the RnR this afternoon (which is written up in this thread http://forums.tdiclub.com/showthread.php?p=1480748#post1480748 )

It's only a 2.64 megabyte AVI, but I can't seem to upload it to TDIClub photo section. If someone emails me I'll send it to them and then theyc an link it up. I would, but I can't seem to access my space at RPI right now.

I think i should drive to Id to get our car worked on nice post wish your shop was closer

Drivbiwire said:

If you have a turbo that is jammed up and causing an Overboost code, you will need to follow the following procedure. To keep the file size to a minimum, I eliminated the removal process and kept it to strictly the repair of the turbo.

This issue is often caused by "Babying" the motor and short shifting at low rpms. People who have this issue are often the ones that have been being gentle with the motor and not following my guidelines of shifting at 2500rpm when cold and at no less than 3,000 rpm when warm.

Anyway, here is what you need to do to fix your turbo:

http://pics.tdiclub.com/data/500/Drivbiwire_VNT_repair_procedure_small.pdf

And when it is all said and done this is how your VNT actuator rod will move!

http://pics.tdiclub.com/data/500/2006_0603_175432AB.AVI

DB

Click to expand...

This is great on how to clean a turbo. Is there a turbo removal how-to somewhere? KL

Never mind...found one.

A variant on the problem on a VNT-20.

Excellent info. I did my turbo today, following it. 130000 miles on UK diesel and it wasn't too bad apart from the clearance under the vanes. Cleaned it all but -- and only when all the cover bolts were tightened -- the actuator was still jamming on the way up. I popped it apart again (much easier the second time!) and I found that there was a lot of wear on parts of the inside edge of the control ring where it sits in the guide rollers. A bit of judicious filing removed the high spots and it now moves smoothly.

[Edit: Added links to photos]
Photos of the split VNT-20 turbo:
http://pics.tdiclub.com/showphoto.php?photo=30529&cat=500&ppuser=52230
http://pics.tdiclub.com/showphoto.php?photo=30530&cat=500&ppuser=52230

Tested thoroughly and limp problem has disappeared. VAG-COM log shows much tighter correlation with spec. pressure.

One other thing - mine is a VNT-20 from an Audi 2.5 V6 TDi. Whilst very similar, this turbo appears to have no alignment peg so reassemble carefully!

Before and after plots of intake pressure

Below are plots of the spec. vs actual intake pressures before and after my cleaning job.
Condition in both cases is 70-80mph and pushing hard on/off to force a limp condition.

I think the plots illustrate the consequences of a sticking VNT quite well!

[Edit: Fixed links]
[Edit2: Pics are now on TDIClub]

Before:
http://pics.tdiclub.com/showphoto.ph...0&ppuser=52230

After:
http://pics.tdiclub.com/showphoto.ph...0&ppuser=52230

Barny-
Your links aren't working, mate.

All-
I finally got around to uploading the video:
http://www.rpi.edu/~morriw/VNTactuation.AVI

Enjoy

OK, I fixed the links. Pics are now on TDIClub.

Before:
http://pics.tdiclub.com/showphoto.php?photo=30525&cat=500&ppuser=52230

After:
http://pics.tdiclub.com/showphoto.php?photo=30526&cat=500&ppuser=52230