Oily inlets

I took the head off my 2.5 nas diesel as it is smoky on start up. I have replaced the valve stem seals but they looked ok. The inlet valves are coked up and oily as are the inlet ports. The engine has the recycled fumes system coming from the sump. Should I replace the cartridge? Or is the engine just worn?

Billy

oil is probably entering through the breather hose, oil is only crudely separated in a simple cyclone,with the oil returning to the sump so there allways be some oil in the inlet and over time they do gunge up,the red blocks and earlier 4 cylinders are known for ring and bore wear but carry on running regardless

Thank you for confirming what I think I already knewJames, I am going to rebuild and start to save and do the job properly. It is a red block 11j. It does run well but has been getting harder to start and smokes at an embarrassing rate on start up. Although it doesn't seem to use oil, which made me think it might not be wear.