About a year ago, when I joined this forum, my daughter's 240D (my car but she drives it at school and basically all year 'round now) was having starting problems. I ended up replacing the starter and motor mounts to fix the hard start problem, but in the process of all that flinging the motor around with the broken driver's side mount, not only did the starter get a little rougher treatment than it was intended to see, but the intake/exhaust manifold studs got elongated. I did not notice this right off the bat, as I was so proud of how readily it would start and how smoothly it ran once I was done, I guess I kind of ignored the exhaust noise.
Well, my daughter can be one of those Princess and the Pea types so when she started complaining about the noise to me over the phone I did not get too worried. I figured she drove some gas car and then hers and just became more aware, or she got some comments from someone about how noisy her car is. Well, around Thanksgiving last year she came home and I ended up taking the noise seriously once I heard it. I found the EGR tube had a hole about the size of a quarter in it. So I replaced it. That made the situation a little better but not much.
Further examination showed the rocking around with that broken mount had also stretched the intake/exhaust manifold studs to the point where the exhaust manifold was loose. A new gasket and new studs solved the probem, but it was a bit unusual to say the least. I have never seen that happen before.
I am not suggesting this is what j22182 is experiencing, just that it is a possiblity. He should check the air cleaner, and the manifolds to see that everything is tight. Once it gets a little loose, the frequency and intensity of the vibrations will fatigue the fasteners in no time. Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)