The Powerstroke 6.0L has a history of mechanical problems including issues with the head gasket and oil coolers. However, the most typical problem is a sticking unison ring on the Garret turbo. This article will explain how to eliminate the sticking by cleaning it.
The Role of the VGT
The 6.0 Powerstroke has a unique variable geometry turbocharger (or VGT). The VGT is unique technology because the effective aspect ratio of the turbocharger is altered as driving conditions change. For example, the best aspect ratio at low speeds is different than that at high speeds. Therefore, changing the aspect ratio keeps the turbo operating at peak levels. One of the moving parts in the VGT is called the “unison ring” and the most typical problem is with the unison ring sticking.
The Unison Ring
The unison ring is controlled by a valve that moves based on signals from the solenoid in the PCM (Powertrain Control Module). The aforementioned valve is connected to the unison ring and the unison ring is connected to the vanes of the turbocharger. These vanes are what open or close based on how much boost is needed. The PCM “tells” the vanes how much to open or close.
What Goes Wrong and Why
The element of the turbo that usually fails is the unison ring. It often sticks due to the way it sits on the center housing. The original design of the turbocharger in the 2003 and early 2004 models are more prone to sticking.
Knowing there was a problem, Ford then made changes to the design of the center section in mid-2004. Where the unison ring sits, the redesigned center section has a beveled edge where the older designs are flat. The inner ring is generally where the sticking occurs due to the tight tolerances. With these tight tolerances, when carbon and rust build up, it causes the rings to seize.
Symptoms of a Stuck Unison Ring
Depending on where the unison ring sticks, you could have different signs that something is wrong.
The ring is stuck closed:
Quick low-end boost
Lack of power at cruise
High RPM
The ring is stuck open:
Difficulty reaching high RPM
The ring is stuck in the middle:
Loss of power but not as noticeable
Lack of response but not as noticeable
Another problem with the unison ring is the keyway slot in the ring can wear in the location where the valve arm comes in contact with the unison ring. This contact causes it to become too large. One other problem is the unison ring could be cracked. Usually, this only happens when someone tries to pry off the ring from the center housing.
Originally the recommendation from Ford to fix the issue of the sticking unison ring was to replace the 6.0 turbocharger. While this is ultimately the best solution, you can also improve performance by cleaning the turbocharger.
The first thing to do is to get a new 6.0L Powerstroke unison ring. You might also need a new VGT (variable geometry turbocharger) solenoid. If your VGT solenoid fails, you’ll see the same symptoms as if the unison ring is stuck.
VGT Solenoid Troubleshooting
Before you replace the unison ring, first check if it is a problem with the VGT solenoid. If the VGT solenoid is bad, that could also make the unison ring stick. If the problem with the sticking unison ring is caused by an electrical issue with the VGT solenoid, this will be shown in the DTC (Diagnostic Trouble Codes) pointing you in that direction.
If it’s a mechanical failure of the solenoid (and not electrical like above) there won’t be a code to indicate that problem. However, the VGT solenoid is easily replaced with a new one without even having to remove the turbo so you could try that fix before moving onto the more difficult task of cleaning or replacing the turbo. The VGT solenoid, as well as the other turbo parts mentioned in this article are all available in our 6.0 Powerstroke turbo rebuild kit.
Removing the Turbo on a 6.0 Powerstroke
Before you can clean the Powerstroke turbo, you need to remove it from the vehicle. This is not the simplest thing to do but here are the steps.
Find the radiator petcock and drain the coolant. Dispose of the coolant properly.
Locate the degas bottle and remove the two bolts and two hoses at the top and the bottom.
Unplug the air filter restriction filter as well as the mass air flow sensor
Locate the FICM and remove the intake tube mounting nuts. Also, loosen the 2 hose clamps for the worm gear. They are located on the intake tubes, one on the inlet of the turbo, one is just after the PCV vent.
Remove the front part of the intake hose assembly from the air filter. Remove the air filter and front air intake. Remove the intake hose assembly which is attached to the turbo. Be aware that the PCV vent hose turns and locks in place.
Remove both charged air cooler tubes. Make sure you pay close attention to the exact location of the clamps so they can later be reinstalled in the same position. Make a reference line to refer to when it is put back together. While you’re in this area, examine the elbow that comes out of the turbo. With age, these tend to crack or split.
Disconnect the VGT solenoid. NOTE: the VGT connectors break very easily. Carefully release the connector with a pick. You’ll notice that there is a metal bail clip that holds the wire to the turbo oil feed on top. Unbolt and remove the turbo oil feed on top.
Loosen and remove the exhaust clamp from the down-pipe. Loosen the up-pipe exhaust clamp. You may need to loosen these with a flat head screwdriver because they tend to stick.
Remove the three bolts that hold down the turbo. Two are horizontal and you can reach those with a wrench from the front. One is vertical and you’ll find that behind the down-pipe.
Using a prybar, gently pry up between the pedestal and the turbo to release it from the up-pipe manifold assembly and the oil drain tube.
Cleaning the Turbo on a 6.0 Powerstroke
Loosen and remove the nut from the housing flange V-band clamp to the turbine housing.
Position the clamp so that it is off the turbine housing and onto the bearing housing in a way that the flange/groove between the two sections is visible.
Apply a penetrating lubricant such as WD-40 or PB Blaster to the turbine housing groove. Let that sit for several minutes before moving on.
Place the turbocharger on a workbench positioned in a way that the turbine housing outlet is face down on the workbench and the compressor inlet is pointing up.
Tilt the turbo to one side and gently tap the turbine housing with a dead blow hammer (not an iron hammer, it will damage the housing). Repeat this until you see a gap form between the turbine housing and the flange while rotating the turbo a little at a time working a complete 360 degrees around the housing. If the housing does not separate, repeat again increasing the force of the hammer taps.
Eventually, the gap will open wide enough that you can fit in a prybar or a large flathead screwdriver and carefully work around the housing until the two halve separate all the way. Work the groove open evenly a little at a time making sure that the turbine housing avoids contacting the turbine wheel as it is disassembled. This procedure takes patience. Separating the housing from the flange is a slow and methodical process. You might try applying more penetrating fluid and stepping away for a while to let the parts soak.
Once the housing finally separates, make sure the turbine outlet is face down on the workbench so the unison ring and VG vanes stay put.
With the halves separated, test that the VG is working properly by turning the unison ring.
Make a reference line on the unison ring with a scribe where the alignment dowel fits into the turbine housing. You’ll need this line to make sure you reinstall it in the correct position during reassembly.
Remove the unison ring and the individual VG vanes. Place the vanes in a container filled with penetrating lubricant. Let this soak for several minutes to loosen heavy deposits.
Clean the unison ring and the turbine housing using 3Ms Roloc (also called Scotch-Brite) surface conditioning discs attached to a pneumatic die grinder. You may need to trim these down to 1 inch in diameter to be able to clean the surface around the VG vane pins.
Clean the unison ring thoroughly as well as any surfaces that may interfere with the unison ring including the bearing housing side, all contact surfaces for the VG vanes, the VG vane pins and any buildup on the turbine housing and bearing housing surfaces. Anything that might interfere with the operation of the VGT needs to be cleaned thoroughly.
Clean the individual VG vanes by hand using a Roloc disc. DO NOT use harsh abrasives, sandpaper or power tools. Also, clean deposits from the pinholes with a copper or brass wire brush.
When the surfaces have all been cleaned, reinstall the VG vanes and unison ring. At this point check for proper actuation and clearance. You want to verify that the unison ring moves freely around the turbine wheel and the flange on the bearing housing. If there is any interference, you will need to clean these again.
Take apart the turbine housing and clean it, the unison ring and the VG vanes with brake cleaner or a similar solvent. Remove any debris that accumulated while it was being cleaned.
Clean the bearing housing side with compressed air (not a solvent).
Lightly coat the following parts with high-temperature anti-seize.
Unison ring contact surfaces
VG vane slots as well as where the slots contact the bearing housing.
Contact surfaces between the VG vanes and the turbine housing
VG vane pinholes
VG vane pins
Surfaces between the outer flange of the turbine housing and bearing
VG control arm pin
Assemble the VG vanes and the unison ring in the correct position based on the reference line you made earlier. You want to cycle the vanes through the fully open and fully closed position several times. After that, remove any extra anti-seize.
Slide the V-band clamp of the turbine housing over the bearing housing flange.
Reinstall the turbine housing to the bearing housing. The turbine housing should be face down so that the unison ring and the VG vanes do not fall out. You should also align the alignment pin located on the bearing housing into the notch in the turbine housing. Also, ensure that the VG actuator pin ins inserted correctly into the unison ring slot.
Adjust the turbocharger so the groove in-between the bearing and turbine housings is roughly the same on all sides. With a dead blow hammer, lightly tap around the entire circumference of the bearing housing to seat the housing. After you tap it a few times the turbine/compressor wheel should spin freely. If not, attempt to even out the groove. The housing should be seated evenly or it will bind.
Continue tapping a little bit harder each time until the housing is seated. Remember to continue to check for binding as you proceed.
When the groove has closed, install the V-band clamp around the flange. Position it in the exact location where you made the reference line earlier in step #6 under the heading “Removing the Turbo on a 6.0 Powerstroke”. Torque the turbine to 160 inch-pounds, loosen and re-torque to 50 inch-pounds. Tap the perimeter of the turbine housing several times to verify that there is no binding. Then torque the clamp to 150 inch-pounds. Do one final check to make sure it is not binding.
Reinstall the VGT solenoid. Torque the bracket retaining bolt to 15 and 18 ft-pounds
Reinstall the turbocharger and test the VGT function.
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comes in contact with the unison ring. This contact causes it to become too large. One other problem is the unison ring could be cracked. Usually, this only happens when someone tries to pry off the ring from the center housing.
