Message or any new Mercedes owner: Do a search of the forum and find out where to get the Factor Service/repair Manual CDs which I am told are around $20. With out it you will greatly increase your suffering!
I was a diesel mechanic for 18 years and while my experience is a big help I still found myself hard pressed to learn enough fast enough to do the fixes that need to be done.
In my case and a lot of other members cases we bought cars that are around 25 years old that other than basic maint. the prior owners did not replace much on the car (because they were built to last) and were selling the cars due to the high cost to fix them. So we are getting the cars that may need some major fixes; sometimes due to neglect or out right abuse. This makes any vehicle harder to work on.
The next thing is the Mercedes seems to need things fixed "by the book" more than other vehicles. This means that you cannot always just go by you past experience and use a proceedure that worked on something else.
Look at some of the threads where even the Mercedes Techs. at the Dealerships have botched their jobs; and them having all the special tools, training and access to repair manuals.

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84 300D, 82 Volvo 244Gl Diesel