the engine has always been kinda clackety since i bought it at 165k. Now its at 175k and the clacketyness has gotten a little worse but over the past couple days it has started to have a real slight engine vibration at 1500rpms. My brother used to have a mercedes diesel and he was saying that the heaters may be bad? I was standing next to it yesterday talking to my old man when i had started it to let it warm up a little and I noticed that it would be running smoothly then all teh sudden the clacketyness will just start instantly...then it will get a little better....but it was a sudden change. I just did a fresh oil change with mobil 1 5w40 with filter and that didnt make any difference. I just dont know much about diesels so I don't know what the problem may be...i figured i knew mostly everything there was to know about engines....but diesels are a different animal.