ZD30DDTi Rocker Cover Removal and Gasket Replacement

[mudski]

It is the original as far as I can tell. But if crankcase isn't vented back to intake, how would IC leaking cause this? Just wondering as not super familiar with this engine

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Oil vapours from the turbo. Remove the IC and see anyway. Like I said if the bottom side of the IC has wet oil deposits, its leaking and needs to be changed. You turbo will be working overtime to create boost pressure that is just leaking out when it shouldn't.
Id check this out first before doing the RC. Because it could just be oil from the IC and not a leaking RC.