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molyneux 04-13-2001 07:15 AM

Regular MB mechanic (from Portland ME area dealer) moonlights and does more involved work on my 77 300D
(late father's Texas car, showroom condition). He says camshafts typically need replacement at about 120,000 miles and that he can hear some looseness in my engine. I also hear a rattle when car is started and before it warms up, but whether this is a real rattle or my imagination (now that camshaft issue has been raised)is hard to tell. Oil consumption is still at about 1 quart every 1,000 miles, or possibly every 750 to 800 miles during hot weather. I still get 28 mpg and understand significant camshaft wear will cut down on mpg significantly.

Another independent MB repair facility owner, in business with factory trained techs for 35 years, tells me differently. He has not personally inspected the car, however. He says that, beginning with the 1977 body model changes, MB fixed those camshaft problems. Older models of diesel engines in the 300 line before 1977 often did need camshaft rebuilds at 120,000 miles. But, beginning with 1977 300's, he generally does not see this to be a problem before 250,000 to 300,000 miles.

So, who do I believe? Is it possible my regular MB guy has his model years mixed up and my camshaft is okay for a long time? Is there anything I can do to check it out for my own piece of mind? One of these guys is wrong, unless my particular vehicle needs a camshaft job at 120,000 miles even though typical 77's can go 250,000 miles. At $1,000
to do the job, I don't want to throw bucks away, but keeping this vehicle in tiptop shape is really important to me. Emotional connection to Dad ...

MB tech wants to do the work about the end of April when he gets back from vacation, so i need some help ...

thanks - Bruce Sanford

stevebfl 04-13-2001 09:25 AM

Sounds like your "moonlighting" friend needs to pay for that vacation. It doesn't matter whether you have an early or late cam, none of them can have their replacement needs diagnosed without visual inspection.

The original 300D cams placed too high of a loading on the rocker arms and they failed early (as early or earlier than 100k mi). They redesigned the rocker arms and maybe the surface hardness of the cams at some point (might be 1977 but I know there was a design change in 1980 also), I think all SDs had the new rocker arms so that would make it by 1978.

Ed Richardson 04-13-2001 08:15 PM

Many of the 77's, through about Feb of 77 manufacture, did have cam failures. I know many replaced in warranty. I had a March factory delivery and had no problem.
As Steve said, the only check is a visual. Ed

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