Turbo gone bad

[EDUB]

I have recently just overhauled all parts of my 95' 6.5TD. I put approxiamtely 4000 miles on while breaking it in. Upon this time I started to notice that the oil pressure was dropping on a weekly basis. Starting it cold I would have a solid 55-60psi. As the weeks and miles went on the OP was dropping to the point I was getting 35psi cold and 10-15psi idleing at operating temp. I decide at this time to stop driving it. The last week I drove it I noticed slight tell tale blue smoke coming from the exhaust. I decide to pull the motor thinking that it was inevitable that I'll have to tear it down again. My first inspection before teardown I noticed that the turbo (that was rebuit with the motor) had about an 1/8" of radial slop in the turbine shaft. Also I noticed in the exhaust there was evidence of oil coming from the turbo. So I'm quite positive that the blue smoke coming from the exhaust was coming from the slopped out turbine shaft pumping oil directly in the exhaust. So my next concern is loss of OP. My next inspection was a compression test and all cylinders had a minimum of 475psi.

My question is would the slop in the bearing/bushing of the turbo shaft show a reduction in oil pressure...?

[Robyn]

If your turbo clearance is wayyyyyyyyyyyyyyy excessive it will allow far more oil to pass through to the crankcase than should and may very well be the cause of the oil pressure loss. The Oil feed to the turbo comes off the top feed of the oil gallery which is also the same feed that the OPS is on.
These are top oilers which is not generally the best design but also they are slow speed engines so its not an issue.
Bottom line. I assume you still have the engine in runable condition in the truck. Plug the oil feed to the turbo and lock the turbo so it cant spin.
Run the engine at idle to warm it up and then see if your oil pressure issue is gone, if so replace the turbo and you are set.
If the issue is still there you need to dig elsewhere
Robyn

[john8662]

Definitly plug the oil line to the turbo for testing. You already know that the turbo needs going through again, so what's it going to hurt?

I hope this is your issue, but am not confident that this is the whole issue.

How have you verified the oil pressure reading, just the factory gauge?

[EDUB]

Thanks for the suggestions... Right now I have the engine on a stand in the garage and it is still completely assembled less the turbo which is in process of being rebuilt-again. Yes, the only OP reading I've taken is from the stock gauge.

What if I ran the oil pump via a drill with the turbo line blocked...?

[john8662]

Ouch!

You already pulled the engine?

I don't think that you would be able to diagnose the turbo being the culprit in the low oil pressure situation with the engine on the stand spinning the oil pump with a drill. Not that it can't be done, it's just that your findings will be inconclusive.

[arveetek]

What if I ran the oil pump via a drill with the turbo line blocked...?

Not without making a special adapter for the rear oil drive. On our diesels, the rear gear-driven vacuum pump or block off plate directs oil to the camshaft. Without the vacuum pump or block off plate installed, a lot of the oil just dumps right back into the sump again. If you have an old style vacuum pump, you can take the cam gear off and make an oil pump drive out of it.

Casey