VNT de-coke by partial turbo removal

[stoocan]

WARNING: THIS PROCEDURE IS FIDDLY, MAY CAUSE INVOLUNTARY SWEARING, PROCEED AT YOUR OWN RISK!

After suffering from frequent limp mode events last summer, I decided that it was time to tackle the dreaded VNT de-coke on my 04 PD 130.

I had read desertstorms excellent writeup on turbo removal here viewtopic.php?f=33&t=33206&p=659278&hilit=turbo#p659278 and I wondered if it would be possible to just split the CHRA from the exhaust housing on the car. After removing the airbox and the air inlet hose, and with bit of exploritory spanner work, and I decide that I could access all the bolts to do the split with the turbo on the car. WD40ed the oil feed pipe nut and ordered the braided hose replacement oil line as a backup. Put Everything back together for another day. Bought a cheap 17mm ring spanner and chopped it with an angle grinder to make a flare nut spanner to counterhold the oil feed union on the turbo.

I had a few days off, so I decided it was time to take the plunge and do the job. The lock carrier was in the service position from the timing belt change that I had done just prior to this, but apart from that I followed all of the steps in desertstorms writeup to the point after the vac reservoir is removed. I had fun trying to get the oil feed pipe nut loosened. The flare nut spanner I had made would not slide down on to the union on the turbo because the tube nut and the union were not exactly lined up. A bit if cutting with the angle grinder ant the spanner was thin enough to slip down to the union, but now it was not strong enough (I could see it opening up as I applied the force). I was about to admit defeat and just destroy the oil line, then I decided to try tightening the nut. I got the nut to "crack" then I was able to undo it relatively easily.

Oil return hose bolts were removed pretty easily from above using a torx bit combined with a 10mm ratchet spanner.

Then I loosened all the bolts that hold the CHRA to the exhaust housing including the three that hold the VNT actuator bracket. Then I gave the inlet/CHRA side of the turbo a firm wiggle to check that the CHRA was not seized into the exhaust housing (it wasn't). Then I carried on and removed the bolts that I had loosened. As some point I decided to remove the actuator, so I got a pick, and removed the circlip, which promptly dissapeared. Luckily I was able to find it on the undertray later. At this point it would be a good idea to mark the position of the CHRA relative to the exhaust housing to aid re-assembly. With all that done I was able to split the turbo:

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Pretty mucky in there!

You will notice the pin from the top left roller is missing. This stayed in the CHRA, and I retreived it from there. I retrospect it would be useful to put a sheet under the turbo to catch any bits that may fall out. The CHRA/inlet was carefully put to the side.

I carefully removed the control ring and the pins/rollers, and then loosened the three torx bolts that hold the VNT mech in Place (note white sheet):

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Do not remove the torx bolts compltely or the little spacers on the far side will drop into the exhaust housing. So i got the VNT mech out and put everything in some oven cleaner.

While that lot was soaking I cleaned up the exhaust housing with small wire brush:

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The bore where the CHRA sits was cleaned out with a pick too.

The VNT mech and loose parts were brushed with an old tooth brush (hand and eye protection required) and rinsed in cold water. They came out very nice:

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Now for the tricky part... reassembly. When you put the control ring back on the VNT mech make sure it is the right way round. The notch for the actuator lever is closer to the vane lever above than the vane lever below. After a few failed attempts and some swearing I tied the vnt mech with fishing line either side, to stop the control ring / rollers etc from poping out of position. Then put the three torx bolts and spacers on and carefully put the assembly back into the exhaust housing. This is fiddly . Make sure that sheet is in place incase anything falls off. Check that the spacers have not dropped off the bolts. Tighten up the screws and then cut the fishing line ties and remove them. Carefully put the CHRA/inlet back into the exhaust housing using the mark you made earlier to line them up. When it is nearly home, wiggle the VNT actuator arm to locate the internal arm with the control ring. It took me several attempts to get the CHRA back into the exhaust housing correctly. If the control ring moves out of position the vane levers will rotate under gravity. You may end up having to take the mech out again and repeat some steps. Make sure the VNT mech is operating freely. If it is not back together correctly there will be some resistance as you move the actuator lever.

Putting everything else back together is pretty straightforward and the reverse of removal.

So is it easier than complete turbo removal? .... well that is debatable. I was not looking forward to trying to remove the nuts holding the turbo to the exhaust manifold, plus the fact that the exhaust housing is bolted in means you can apply a bit of force to dislodge a corroded in CHRA if required. Certainly it is fiddly getting the thing back together without gravity assistance to keep everything in place. I will leave it to the readers to discuss. That being said it can be done this way, and the car is running well again.