Question about oil in turbo

[Chris611]

Today I noticed quite a bit of oil that seems to be going into the turbo. It comes from the passenger side valve cover. There has always been some, but now there seems to be more oil. What does the "can" do that sits on top of the valve cover do? Looks like there is a spring in there, I wonder if that is worn out and letting excessive oil go into the turbo.

Its a 1997 K2500.

Thanks
Chris

[BobND]

The oil is from piston ring blow-by carrying crankcase oil along with it as it exits the crankcase though the ventilation system.

The "can" is the CDR (crankcase depression regulator). Essentially, it is normally wide open, allowing combustion products from the crankcase to feed into the turbo inlet.

If the air filter were to plug, the resulting negative pressure at the turbo inlet would tend to draw a significant vacuum in the engine crankcase, possibly pulling in dirt by the crankshaft seals, and worse yet, trying to draw even more oil out of the engine, into the cylinders, which could lead to overspeed and/or loss of lube oil. Under those conditions, the negative pressure on one side of the diaphragm in the CDR allows full atmospheric pressure to act on the other side of the diaphragm in the CDR, which moves, acting against a spring, and closing off the crankcase from the turbo inlet to the degree needed to prevent a negative pressure from being drawn on the crankcase.

There is metal mesh in the RH valve cover that does a poor job of removing oil from the vapor stream leaving the engine.

Some engines have a centrifugal separator setup that spins the oil mist out of the crankcase vapor, and keeps the oil in the engine, but our favorite GM diesels depend only on the ineffective mesh to remove the oil, and the spewing out of crankcase oil only gets worse as the engine wears and develops more blow-by.

[Chris611]

Thanks. What is the part number of the CDR for a '97 6.5L. I have searched in cdr posts and also searched gmpartsdirect & rockauto. I don't feel confident that the part numbers are the right ones. Can someone let me know what gm part number to order?

Thanks
Chris

[BobND]

Chris,

Not to discourage you, and I know there are those who will disagree with me, but I've never seen replacing the CDR help with the "oil in the turbo" problem.

I HAVE seen the CDR diaphragm fail so that oil leaks EXTERNALLY from the CDR.

The part numbers appears to be 2509 8706, @ about $70.00 LIST.

Good Luck!

[Chris611]

Thanks BobND.

What does the oil leaking externally mean? You mean out of the various seals around the engine? From what I have read on posts about the CDR, there should be an oily residue in the can and tubing, but not a lot of oil. The other day I pulled the CDR and the metal tube that goes to the turbo as one piece and where I sat it on the ground I had a small puddle of oil that drained out of the metal tube. Maybe a tablespoon or so. From what I read, this is excessive to come out of the CDR. Maybe I misread or misinterpreted those posts. Let me know what you think.

Thanks
Chris

[jkpyper]

I think what he means is that the job of the CDR is not to prevent oil from reaching the turbo, it is to vent the crankcase. If too much oil is being vented from your crankcase, it is not the fault of the CDR it is most likely due to too much oil getting vaporized in the crankcase of the engine. The CDR is still doing its job of venting the crankcase but it doesn't know that there is a lot of oil in the vapor. The solution is to find out why there is alot of oil vapor in your crankcase. In my case, it was because of a cracked block.

If GM intended to prevent oil vapor from reaching the turbo, they would have installed an oil/air seperator somewhere in the system.

[rameye]

I just happened to be researching a turbo problem in my ride....the service manual states that when inspecting the turbo...oily residue is not cause for alarm.

[BobND]

Originally posted by Chris611:
Thanks BobND.

What does the oil leaking externally mean? You mean out of the various seals around the engine? From what I have read on posts about the CDR, there should be an oily residue in the can and tubing, but not a lot of oil. The other day I pulled the CDR and the metal tube that goes to the turbo as one piece and where I sat it on the ground I had a small puddle of oil that drained out of the metal tube. Maybe a tablespoon or so. From what I read, this is excessive to come out of the CDR. Maybe I misread or misinterpreted those posts. Let me know what you think.

Thanks
Chris When I mentioned the CDR leaking externally, what I meant was there is a small vent hole in the crimped-on cover that allows atmospheric pressure to act on the backside of the diaphragm in the CDR. If the diaphragm cracks, tears, leaks, whatever, oil will ooze out of the vent hole in the CDR.

Once again, the purpose of the CDR is to remain wide open at all times, to allow the crankcase to vent into the turbo inlet. The only time the CDR will be anything but wide open is under conditions of a restricted air filter, or POSSIBLY maximum engine speed and power, if the inlet pressure to the turbo were to go negative enough that it begins to draw a vacuum on the engine crankcase.

When there is excessive engine blow-by, the only way the oil mist gets separated out is buy the steel mesh in the valve cover. The CDR is NOT designed to prevent the oil from reaching the turbo. The oil mist from the engine simply passes through the CDR.