Background: I bought this thing in the summer of 2007 with 7900 miles on it. I've always put Rotella T6 and WIX filter in at the 3,xxx mile reminder interval. In October of 2007 it got a new warranty turbo (I think because a glow plug tip went through the exhaust turbine and ripped off a couple vanes) but otherwise I've been doing everything possible along the way to generally keep it running well.
Anyway, now at 162,xxx miles I'm having real turbo issues, so thought I'd post up some info for consideration. It started with not being able to floor it for long periods of time (over 4-5 seconds) without throwing a P0234 code and going into limp mode. One cold day it started up and was billowing white smoke like crazy. Drove off and 1/2-1/3 mile down the road it cleared up. Happened a couple of other random times, but not consistently. Then it started throwing both P0299 and P0234 at the same time just cruising around town. Checked all the typical suspects, MAP, vac solenoid, vac modulator, filter, hoses, all fine. The turbo vacuum actuator arm could only move up and down about 1/4" or so. Tried doing the "Italian tune-up" routine at a local rural road that goes up a mountain. With the DRB I would clear 3 limp modes on one pass up the mountain. Must have done that for 3-4 runs up the hill. Didn't fix it. Pulled hoses off enough to grab the intake impeller stud and could wiggle it and it would make a noise like a "click", and the rod still didn't have range of motion.
Now I have the thing apart (with a new upgraded Sasquatch turbo on the way) and have made a few observations. Wiggling the impeller, it can go side to side radially from housing wall to housing wall, and it has axial play as well. The bearing system is shot for sure. Took it apart and inside the bearing cartridge stunk something horrible, probably burnt oil. There is a heavy thick oil paste coating the interior compressor housing, and there is residue inside the CAC hose, all probably due to the seals failing from the bearing wear. The hard oil supply line had a "burn" spot right where it passed vertically by the exhaust manifold. I think the oil in the supply line gets cooked right there. The metal tube had a very dark rusty patch right there facing the manifold. In an attempt to fix this situation, I sandblasted the tube, powder coated it, and sleeved it with a high temperature braided sleeve.
Then, I looked into why the VNT actuator wouldn't work. Took the cast exhaust housing off the cartridge, and found the area where the actuator finger, VNT fingers, and common actuation ring were was full of crud. This is an area that is a bit of a "dead end" where exhaust does not flow through, but can allow accumulation of crusty crud to build up and stop the movement of the mechanism. The VNT fingers were encased in crud. The vane side of the that assembly where the exhaust flows was relatively clean (just dry soot, expected of an exhaust surface) and clearly not the cause of the problem. No amount of high RPM runs was going to fix this. You can see the crud I'm talking about under the turbine wheel that I didn't clean off. That is in the same chamber as the VNT fingers and ring.
Just for grins, I took the VNT assembly out and sandblasted the whole thing, and it's as free as a bird now. With this chamber design, it seems this sort of thing could happen again, with no remedy other than full disassembly and internal cleaning. If you took the exhaust pipe off and shot oven cleaner in there, it's still not getting into the finger chamber. I think I'm going to take the new turbo apart when I get it and high temp Cerakote those parts.
Somehow, I'd like to improve upon this design while I have it all apart.
