As I only have the car a few months I can't honestly say. but so far fan belt went. and 2 new tyres.
She doesn;t burn any oil, was well cared for by previous owner, but has a slight leak around the head. turned out to be a tapet. something I believe pretty common with this car. engine very reliable.
But she has a few bizzare gremlins. for example. when I put on full lights. the wipers come on and wipe twice. the same happens when I indicate right when fogs are on. some time windscreen washer are a bit lazy. but really these are all minor. compared to the 1998-2005 model.
Plan to keep this car a few years. as a hobby car. as she has plenty of life still. and no rust and full service history from day1.remember she is not japanese.!!! very comfortable to drive and travel in. but needs great care. power is fine. she is never under pressure. great on long runs. which I do 300-600 in a weekend. main reason I bought is the safety. evening though the design is now almost 20years old. I will see what she is like in a years time. what has failed and what has not. but generally engines and gearbox strong. pre 98. I thing the quality and materials used are far superior to later benz. one of the last good ones.
Have had 2 e class before and c class and new s. this is so much better.
I now have the car over 6months and is going super. it now has over 120000miles on it. minor rust bubbles appearing on arches, but easy to sort if treated early.
Recently had car serviced. full service. needed new rear dampener. as the bushing had worn it. new rear brake pads, and cooling pipe. parts can be expensive, but if you get someone who knows what they are doing with these cars, life is so much easier. by the way the wiper problem as mentioned earlier was a relay problem. sorted in 10 minutes. if anyone has problems with the electrics I recommend a visit to a bosch specialist. they have the problem sourced/sorted in minutes. depending on the nature of the problem. really a great car.