What have we learned. Blowing the Carbon out of the Cylinders by cranking the Engine after reaming the Glow Plugs is in some of the Official Mercedes Diesel Service Manuals.

Next doing that apparently causes no harm because it has been done for I don't know how long with no issues.

If you don't want to blow out the Carbon out of the Engine by cranking the Engine then don't do it.

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84 300D, 82 Volvo 244Gl Diesel