Turbo internal oil leak: supply vs return psi

Gypsy62 · **Posted:** Tue Sep 03, 2019 3:59 pm

Doing protracted & fairly excruciating battle with blow-by @ two sequential "newly rebuilt" replacement turbos.
My original had >150k miles and was blowing (maybe a pint per 500 miles?).

I have learned the hard way to leave the CAC hose off a newly-installed turbo in order to permit viewing into the turbo during brief post-op startup to inspect whether the spindle is blowing oil. Both replacement turbos have.

I am wrestling with the diagnosis. My basic conclusion is "bad luck", and that the two "newly rebuilt" turbos I sourced have both been defective.
The latest turbo (vendor="Dieselsite") is blowing only a 1/4 of the previous:
I only observed the internal leakage for about 30 seconds; is it possible/normal that the turbo's spindle seal needs a bit of time to seat? Is 'a bit' of initial startup leakage normal, maybe before heat-expansion?
Should I sew-up the intake system and drive it for a bit and then re-check?

-ALL supply/return tubes are clear w/properly seated seals & gaskets.
- The PCV output-hose is removed and free-breathing = crankcase airflow is confirmed.

Question:
How could the crankcase pressure at the turbo return/drain tube (@ <10psi w/ venting PCV) compete with the ~20-60+psi (rpm-dependent) of the oil-pump pressurized turbo supply tube? At what pressure-point does crankcase pressure at the return tube exert enough force to stress the turbo's spindle seal to internal leakage?

Insights and opinions appreciated.

[Keys: CRD turbo leaking, turbo blow-by, new CRD turbo bad faulty failing failure smoking ]

WWDiesel · **Posted:** Tue Sep 03, 2019 11:31 pm

I know we keep beating this to death!
But your CCV hose should be connected to the turbo inlet to pull a negative vacuum on the engine crankcase. If was designed by the engineers to do this!
Some on this forum have reported either a blown or leaking oil seals when they ran without the CCV connected to the turbo inlet boot (EHM)
Reminder; the vacuum pump on this engine discharges into the engine crankcase internally adding to the internal pressure along with whatever blow by you have form the piston rings and all this add greatly to the flow loading of the CCV system externally.
See this for plenty of reading on all the reasons NOT to run the CCV to atmosphere:> viewtopic.php?f=5&t=80491

Just as a second thought, are you sure there is no obstruction in the turbo oil drain line or where the drain line connects into the block?
The drain from the turbo should basically be an open drain back into the block with no restrictions.
After two turbos leaking, I would be darn sure that the drain has no issues and I would connect that CCV back to the turbo inlet boot to ensure the suction from the turbo is pulling a negative vacuum on the crankcase when the turbo spools up. (Same time as the oil pressure would increase due to increased RPM's.)

Keep us posted! :POPCORN:

NOTE: Many install a Provent coalescing filter to filter and catch oily liquids to remove them out of the CCV vapors before they enter the turbo inlet pipe.
viewtopic.php?f=5&t=83541

Gypsy62 · **Posted:** Wed Sep 04, 2019 1:22 am

I'm reasonably versed in the posts you've mentioned.
I installed a non-provent filter/catch-can setup which reasonably replicates its function and breathes quite freely.

I confirmed that the turbo return tube flows freely into the block.

I absorb the importance of the "active-vacuum" factory design. With the SasQ 1&2 in place I am trying (like others before) to further purify and cool the intake-air path.

To review the components vulnerable to elevated case pressures:
- Crank/cam oil seals
- Valve guide seals
- ..." ?
I'm still hoping for knowledge regarding how the opposing forces of the turbo return tube's crankcase "back-pressure" versus the opposing oil-pump pressurized supply-tube could result in an internal turbo spindle leak.

Tomorrow I'm going to remove the turbo return tube from the block and route it to a jar for a brief test-run. If there's little or no pressure blowing oil out of the opened case-hole I will have a very difficult time swallowing that somehow crankcase pressure is causing the serial leakage at the turbo spindles. However, if there's significant pressure blowing out of the case I'll own it and report it.
After all, my objective is a dry turbo not a shiny pride.

Re pcv/catch-can return routing, in order to replicate the turbo-intake active-vacuum I'm considering installing a "Y" into the exhaust downpipe after the turbo exhaust outlet. In order to create a venturi-vacuum effect, the tap might have to be angled to point downstream (vs absorbing exhaust pressurization). No muffler, short pipe... I opted for a Cat but as long as it's clear any competing back-pressure should be minimal. I'm no engineer but it seems logical.

Further, the 3" cat (3" exhaust mod) would subject the case fumes to some emission-reduction outbound (compared to venting to air).

Loco is as loco does.

WWDiesel · **Posted:** Wed Sep 04, 2019 2:35 am

Yea I know, kinda beating a dead horse! Sorry. :banghead:

No one has ever posted anything about seeing any valve guide wear or seal issues of any significance. At lease no one has reported it.
The oil pressure feed line to the turbo bearings comes straight off the main oil pump discharge galley.
So unless there is an orifice in the feed line, those bearings are getting some fairly good oil flow when the engine RPM's come up thus increasing oil pressure.
But that leads us back to the drain system off the turbo bearings. If there is any restriction downstream of the bearings that would allow back pressure to build and put oil pressure on the bearings and their seals.
I certainly do not profess to be an expert on the turbo internals and I defer to some on this forum who have taken them apart and know what is inside them and how the oil feed and drain functions inside them.
But in my humble opinion, there should be no oil leakage coming from the turbo bearings oil seals. Just does not seem logical or many would be reporting it.
So back to square one, what is causing them to leak? :juggle:

Gypsy62 · **Posted:** Wed Sep 04, 2019 5:06 pm

Dry.

I was not enthused about executing the return tube removal test. Those of you who have R&R'd a CRD turbo are aware how much FUN it is to dance with those 2 bolts...

Instead, I decided to let the "new" turbo warm-up for awhile and observe the oil flow at the turbo's compressor output(CAC-feed).
[Tip: you can dummy-in the airbox directly to the CAC using the accordion hose = adequate air-filtration while exposing the compressor-side of the turbo for visual inspection while idling]

After about 20 minutes I viewed the turbo throat: DRY. I even brought up the throttle to 2500 for a minute and then re-checked at idle; dry. Holding a paper towel over the turbo output for a minute, zero oil splatter.

While idling, I then experimented with glove-plugging the pcv intermittently to boost the case pressure (with spanking-new front/rear seals, not excessively).
Result while viewing the turbo throat: dry.

Conclusion:
- The Crankcase pressure back-feeding up the turbo return tube was NOT causing the oil blow-by at the turbo spindle.
- Cause: The turbo's spindle-seal just needed an initial dose of operating-temperature heat to expand the internal seal sufficiently to halt the cold-turbo blow-by.

Thanks for the input!

Gypsy62 · **Posted:** Wed Sep 04, 2019 5:09 pm

Regarding the FIRST replacement turbo, I can safely conclude that merely warming the turbo spindle would not have halted its blow-by. Post-op I test-drove the jeep for at least 30 minutes: the exhaust smoke just worsened, and after 15 minutes it was burning so much blow-by out the turbine/exhaust side that people were yelling that my car was on fire, lol.
Fortunately, I haven't yet installed the 3" Cat; that volume of buring oil likely would have killed it.

I just ordered the Provent. Although I trust that my substitute setup similarly vented case pressure, I'll concede to their engineering and thermal durability.

I'm also going to dig up the old egr tubes and see if anything can be re-purposed towards the previously-described pcv vent-return exhaust downpipe insertion mod.
After completion, I'll throw a vac gauge on the provent's output hose and report whether there's any venturi vacuum-effect (and amount).

Finally, three years ago when I did the rockers, head gasket, ARP's, etc., I should have rebuilt the short block. Time, tools, money, health and sanity were all decisive factors, but now I am pining for a fresh bore and rings.
La Vida.

Time to sew it back up and actually enjoy USING the beast.
Remote Baja beckons : ) .

WWDiesel · **Posted:** Wed Sep 04, 2019 10:38 pm

Glad you got it sorted out and it was not a turbo or drain pipe issue. I know those drain pipes are a PITA as described by many on this forum.
Good move on the ProVent install! :rockon:

Have fun in Baja... :JEEPIN:

Turbo internal oil leak: supply vs return psi

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