Degrease the area and above it and locate exactly where the leak is coming from.

If you removed the Expansion Joint near the Trubo and look in side you should see flat black colored carbon. If the carbon is shiny/wet looking you are getting Oil from the Turbine Seal or the Oil is coming out of the Engine and getting into the Turbo.

If you find the shiny carbon removing the turbo will allow you to see if Oil is in the Exhaust Manifold as it will also have shiny carbon in it. If the Exhaust manifold has that dry carbon you know it is the Turbo that is leaking Oil.

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84 300D, 82 Volvo 244Gl Diesel