I have worked on diesels for over 30 years but this thread and another recent one in which you posted similar information (ref: faulty MAF) has made me think about something I took for granted. I have never questioned as to how air is regulated in a diesel engine until now. Apart from that the purpose of the egr seems to be what I was always led to believe and your post seems to confirm what I have said but in a more technical manner. What I would like to ask though, and your post doesn't seem to answer this, am I correct that the AFR being lean causes higher combustion temperatures? That is why I asked about disabling the egr on my own vehicle as I was told on a course some years ago that one of the causes of vehicles overheating under cruise conditions could be a blocked egr. This was however, quite a few years ago when things were a bit simpler, excluding me of course
Regards, Bryan.