VNT turbo disassemble replace and repair stuck vanes
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Introduction
This article shows how to disassemble the VNT mechanism for cleaning. Note - turbo housing removal and VNT disassembly requires at least basic mechanical experience and tools. You are not disassembling the turbo CHRA so you don't need to index the wheels or balance them. Basic definitions: CHRA - center housing rotating assembly - this part holds the oil fittings, bearings, and turbo wheels. Turbine/intake side is the aluminum side. Compressor/exhaust side is the cast iron side. For more details on how a turbo works and parts, see 1000q: turbocharging FAQ.
The VNT lever on the outside is welded to a lever inside the turbo housing.
This lever rotates the ring inside the turbo and moves the VNT vanes. See the below videos to see how
smooth and free the lever should move. It should not stick or bind at
all. Vacuum is being applied to the can, not pressure.
Here is how the lever and ring move the vanes.
Procedure
Remove the turbo and cover the oil feed and drain lines. I also suggest covering the compressor side openings with tape and cleaning the exterior of the turbo.
Remove the actuator (2x 10mm) bolts and remove the circlip holding the VNT
lever to actuator rod. I suggest getting a spare clip since these can fly
off during installation.
The turbo housing will be rusted to the CHRA so soak the exterior of the turbine side in PB Blaster or liquid wrench. Tilt the turbo and fill the inside of the turbine side with PB Blaster too. This will penetrate the joint from the inside and preclean/loosen a lot of the soot buildup inside. Let it soak for a while and tap it to help the lubricant penetrate. If it's really stuck then let it soak overnight.
Once it's soaked and penetrated, you may notice that the VNT lever may move freely. Don't be fooled into thinking "problem solved" because the ring inside sticks and it's range of movement won't clean the area where it sticks - you'll still need to disassemble the turbo to clean it. Remove the 5x 10mm bolts holding the housing to the CHRA. The two bolts without washers hold the actuator bracket.
Now separate the turbine housing/exhaust manifold from the CHRA. The
joint is highlighted with a dash red line below. The same location is
highlighted with the same red dashed line in the second picture. It's a
machined fit and difficult to remove because it will probably be rusted
and seized. Try heating the housing with a torch (not the CHRA section)
to expand it.
In the next 2 pictures you can see each side of the CHRA and housing and
where they mate. Again, the red line in the pictures above and below show
where the joint is.
Tap with a rod and hammer or a 90o pry
bar (to get more clearance around the housing) on the cast iron of the CHRA
on the intake side - do not hit the aluminum. Aluminum is a soft metal
and you could damage it by hitting it. Highlighted in red below are areas
where you don't want to hit. The intake side of the CHRA or the areas
highlighted in
green are where I suggest you tap. Be careful to catch both sides when
they pop off since it could damage the turbine wheel if it comes off with force
and hits the turbo wheel. You may find that it's seized so just tap repeatedly and head the cast iron
housing until it separates. This may take a while, just be patient and
keep hitting the CHRA/heating the exhaust housing until it begins to come
off. If the cast iron cracks you will have to replace the turbo but stuck
VNT vanes would have required turbo replacement anyways. If you really
can't separate the turbo, see if it's still sticking after soaking it internally
with PB Blaster and manually moving the VNT lever back and forth. If it's
better you may want to clean it as much as possible and just put it back to
avoid cracking the
cast iron. You could find a local turbo/performance shop and have them
separate it but I doubt they would guarantee no damage.
Once the turbo housing is off, note the white arrows below where rust and buildup around the circumference
of the ring cause it to stick, especially on the raised part of the ring that sticks out a little
more. This is why PB Blaster can't free the ring in serious cases - the
ring can't scrape those areas clean. The
yellow arrow indicates the machined flange where the housings mate.
Remove the 3 alignment dowels and their spacers. Now pull off the rotating ring.
Below is another picture after
cleaning. The next few pictures with the white "up" arrow are all
taken in the same perspective for clarity.
This ring is the part that gets
stuck. The ring has an empty slot for the VNT lever on the CHRA and shorter and longer
holes on the sides. These holes show how the ring
should be oriented during assembly. There is also a hole for the alignment pin on the
CHRA - note it's position as well. The pin ensures that the CHRA and housing are
aligned during reassembly.
Inspect the empty slot and the lever for wear.
Here you can see the alignment pin on the CHRA which goes into the
hole. It's on the lower side of the picture because when the 2 halves are
facing each other and assembled it will be on the upper side of the
picture. Clean this side but make sure to not hit or spin the turbo
excessively. You can manually move it but don't point a pressure washer at
it. Don't put the CHRA in a parts washer since the oiled bearings need to
stay clean. Do not try to remove the turbo wheels. Carb cleaner and
a rag will clean it very effectively.
At this point, stop and evaluate the condition of the rest of the turbo. Since you soaked the inside with PB Blaster, much of the carbon will be dissolved. Clean it as much as possible and put the ring and spacers back on. If the problem was a sticking ring and it now moves smoothly AND the inside of the turbo is sufficiently cleaned (backflush the manifold and clean between the vanes too), reassemble the turbo. The less you mess with, the less that can go wrong. If you got it working, don't continue to fix it until it's broken! A little liquid or bits of carbon will get burned up once you put everything back together and run the engine. The exhaust may be smoky after initial engine startup.
If you determine that it's still not moving smoothly or that the area between
or underneath the vanes is still dirty, continue disassembly. Remove the 3 T-20 torx bolts pictured below, the upper right one has already
been removed. This will release the VNT vane
assembly - remove it.
Underneath
are 3 more spacers. If the torx screws don't want to come all the way out,
just make sure they're not holding the assembly down and the vane assembly will
come out. These spacers are taller and have a wider hole than the alignment dowel spacers so they can't be
mixed up.
The flat plate/ring underneath can also be removed but don't force it.
Since the VNT vanes ride on it, you don't want it to be scratched. Carb
cleaner will clean it effectively.
Pressure wash or scrub the exhaust manifold/housing clean. It's cast
iron so don't be afraid of giving it a thorough scrubbing. Again, make sure
to clean the area around the rotating ring so that it can rotate freely and
smoothly and avoid scratching the VNT vane surfaces. Use a pick or emery
cloth (very light grit sandpaper) to clean
the corners. If the ring pictured below comes off, index it's position to
the manifold and scrub off any rust underneath it.
Clean the other parts with carb/brake cleaner. If the vanes have burrs on the edges or scratches, smooth them out.
Assembly is the reverse of disassembly. Apply some high temp anti-seize to the 3 torx bolts and make sure they are through their spacers. Exhaust gasses could reach peak temperatures of 1500-2000oF so make sure the antiseize can handle it. (The reason the car doesn't melt is because the full heat of the exhaust gas isn't instantly transferred to the metal). Don't tighten them too much or else it could compress the spacers and bind the VNT vanes. I don't know the torque of the 3 bolts but the vanes should move easily without binding. Check the movement of each vane. The pointy end of each vane should face inward. See the videos above for an example of VNT movement.
Replace the rotating ring noting the empty slot and the longer/shorter hole and the alignement pin as pictured above. Replace the alignment dowels and spacers. Apply a very thin coat of high temp antiseize to the flange where the CHRA and housing meet.
Gently slide the CHRA back into the housing, noting the alignment pin. Apply antiseize to the 5x 10mm bolts and replace. Manually move the lever back and forth to check for free vane movement. The rest of installation is the reverse of removal. As noted in the first picture, a 1/4" e-clip or circlip can hold the VNT rod onto it's lever.
To ensure adequate lubrication, put some oil in the turbo oil feed union and let the engine idle for 1 minute before revving.
Have more questions or have some tips? Post your comments in the myturbodiesel.com forums.