Hi everyone.. New to the forum.. I had a 244 DIESEL in college with 280k miles which was by far the best car I ever had.. I now have a 1988 740 GLE with 163K on it. I bought it from the 2nd owner who changed the oil religiously. He did, however, have 3 boys who drove the car through high school and college. Now for the problem....The engine has a fairly loud knock that does not go away when warmed up. I don't hear it on a cold start and it begins approximately 30 seconds after. It sounds to me like a rod knock but I had a friend who is a mechanic and Volvo enthusiast tell me it was the upper end and not to worry about it. It seems to be the frequency of half the rpm. Has anyone ever heard of a fairly loud, consistent knock coming from the upper end of this motor once warmed up???