CM871 turbo premature bearing failure

[Mrkentee]

Replaced original turbo at 600k. Stuck VGT.
Cummins reman lasted about as long, but I noticed a little excess play in shaft, so to be safe replaced with reman from turbo place in Ga.
After 13-14 months started letting oil by the seal. No warranty after a year.
Rechecked all usual suspects, lived with it for 6 months and replaced with one from a turbo place near Chicago. Problem solved?
A few days ago, the bearing on this one failed after 23 months.
Demandated since 2016. This program since 2019 by a trusted member of this forum. No blowby to speak of. Not aware of any boost leak, but will test again when I get home. Oil lines are clear.
I got another one overnighted to me and changed it in a truck stop, but I’m jittery now. Is this just something you have to live with on remans without spending over $7000 for Cummins reman?
The Chicago company is well thought of by a well known shop. Part of the reason I used them.

[tree98]

Are you sure your not building up crankcase pressure? Your ccv filter is drilled or replaced with maintenance free ? Make sure there's no obstructions blocking pressure release anywhere. Are you getting good oil feed into the turbo? With the turbo completely off the truck, start it up and see if it's strongly spraying oil out of the feed tube, maybe its partially collapsed inside or who knows??

[Mrkentee]

(03-15-2026 )tree98 Wrote:  Are you sure your not building up crankcase pressure? Your ccv filter is drilled or replaced with maintenance free ? Make sure there's no obstructions blocking pressure release anywhere. Are you getting good oil feed into the turbo? With the turbo completely off the truck, start it up and see if it's strongly spraying oil out of the feed tube, maybe its partially collapsed inside or who knows??

Filter is maintenance free AND drilled.
I blew through the oil feed line and drain, seemed clear. Couldn’t get one, but will replace at home.

[marek4792]

That Chicago place isn't what it panned up to be, they always leaked oil whereas my OEM turbo on the truck now isn't passing oil..

[Rawze]

some things to know...

== There SHOULD BE up to about 0.045" side-side play in a VGT turbo if you press on the shaft hard to one side and the other.

VGT turbo (actually any holset turbo) ... WILL LEAK OIL out of its face if there is ANY crank case fumes buildup ... I.E.> high enigne blo-by, or even slightly clogged crank case filter. They typically are NOT a perfect seal.

Air inlet restrictions and a lot of idling can cause turbo to bleed oil too. - All normal.

Turbo shafts do NOT use rubber face seals. They use turkon-style seals that are a loose fit. This is so the shaft can spin 120,000+ rpm and not get cut or get excessive wear by the seal. There is also not any oil pressure behind the seal.. it is leak oil from the crank case. - Hence, Any crank case pressure buildup (which there should be none) will make oil pressure at the turbo face seal causing it to bleed.


You say your CC filter is is drilled out... when is the last time you took it apart and verified it was not completely rotten in there and can still breahthe really good?.

when is the last time you verified that the tube after it is not getting clogged with shmoo or dirt?.

Also,... What is the max boost you see in a hard pull / what positions is it going to?.


Crappy chicago after-garbage turbo or not ...

I.E.> It is NOT normal for multiple turbos to become leaky like that unless you have blo-by issues or oil flow problems.

I.E.> it is ALSO VERY NORMAL to have side-play in the turbine on inspection (up to 0.045") which can be felt.

Could it have been that your first replacement was perfectly fine and you replaced it again not knowing any better due to other circumstances?.

just some thoughts.

[Mrkentee]

Replaced 2nd turbo proactively in ‘22 because I could touch the sides with the blades on inspection. Replaced with Ga turbo that was fine but started leaking oil.
Replaced that with Chicago turbo that stopped the leak. But the bearing failed after 23 months. It was not leaking oil.
I just cleaned the cc filter housing out a week or so ago. It was fine. I will double check all that.
I try to limit my boost to 30 or a little above. It can do more. Keep rpm’s 1500 or above.
It “seems” like it just failed. I will check further, as I want to know if there’s something I need to correct. Or are they using junk parts, and I just got one that couldn’t take it?

[tree98]

On the Chicago turbo I would definitely blame junk parts. What exactly do you mean by "the bearing failed" what exactly happened?

[mikkhh]

Little felt up and down play on turbo is perfectly normal even on brand new turbos, oil pressure will center the shaft while spinning. Axial (in out) play on the other end is bad and points to a worn bushing.

Most turbo rebuilders in my area just sandblast and clean housings, replace actuators with chinese ones and use turbo parts from mel ett (some more brave ones just buy absolute no name garbage chinese turbos, which are junk). Those do not last as good as well as an used working replacement. On cars the turbo and vgt lever have to be paired together (max position stop screws set).

[Mrkentee]

(03-15-2026 )tree98 Wrote:  On the Chicago turbo I would definitely blame junk parts. What exactly do you mean by "the bearing failed" what exactly happened?

Started a loud humming with no boost. Blades were rubbing against the housing. Wobbling all around.

Also, what’s weird is, they don’t want the turbo back, only the actuator. For a $250 core charge. That actuator was new in ‘22. I might just keep it.