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2,000 engine hours. 120k miles. P0299 Code, so I pulled the turbo for cleaning. Vanes look great, but unison ring frozen to housing hub. I'm cleaning everything up before reassembly, but I'm wondering about the slits in the unison ring. Are they supposed to be perfect ovals or are they supposed to be wider on the ends of the slit and narrower in the center (see photo).
Mine did too. I was advised to replace it by the fleet mechanic at my work. I should have to turbo back in this weekend, we'll see if it gets rid of the studder under heavy load.
Flip it over? I know that sounds like a farmer solution, but... I'm guessing mine ovalized because the actuator pin was working hard to rotate the frozen unison ring. So... if I flip it over so the pin has a nice round hole rather than a worn hole, that should work for another 80k, right?
My assumption is that by 200k miles, something else will fail (oil cooler, EGR cooler, HPOP, etc) which will require pulling the turbo again in few years. I could inspect the unison ring again at that time.
If I replace the unison ring, where do you recommend that I source a quality replacement part?
edit: I'll take and post a photo of the backside of the actuator hole.
-Mike
Last edited by IHbase; May 16, 2020 at 02:54 PM.
Reason: additional information
That's just what mine looked like. After I get the turbo back in, I'll let you know if it cures my surging under load.
I picked up the unison ring on ebay (motorcraft) for $50 so if doesn't cure it, I'm not out much.
Thanks. I'm interested in your answer. Hope it cures your issue.
If your turbo has been out before, you might check to be certain the actuator piston is clocked correctly. Diesel Tech Ron (RIP) posted a nice YouTube video on how to check and clock the plunger with the rotating actuator pin.
Mine has been out a couple times for a y pipe replacement and an oil cooler, but never taken apart. I'll check out Ron's video, thanks. I did mark the position when it took everything apart to make sure everything went back correctly.
I'll keep you updated.
Well, it's all back together and I took it for a test drive.
The issues that i was experiencing was around 10 psi boost, i could hear a faint flutter, if i backed off or gave it more throttle it went away, this i could never feel like a surge or studder.
Second, while pulling anything over 5000 lbs around 20-22 psi boost I could feel a surge or studder until I backed off or gave it more throttle.
The last thing was starting it up after it was warm, for about 45 seconds I had what sounded like an exhaust leak. This was probably just that from when I replaced the y pipe.
So far, the faint flutter and the exhaust leak sound are gone. I haven't pulled a trailer yet to determine the studder. I also noticed that the vein sweep sounds sharper and more crisp.
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