All this caused by lack of servicing!! These images are of a D22 2.5ltr Nissan Navara with 114.000klms. The vehicle came in for diagnostics, it was blowing a large quantity of black smoke.
What we found: The air mass sensor was very dirty and the air cleaner was filthy on the inside of the filter. The top of the engine was full of a thick black sludge. The injectors were tested and were found to be over fueling from premature wear.
It just goes to show that good quality filters, oils, and regular maintenance is vital for the longevity of any diesel engine.