My 92 400E has about 200k miles. At 100k, if well maintained with regular oil changes I would not recommend anything out of the ordinary. I waited until 190k to get a timing chain and guide rails. This was "just in time" I was told. I would agree with the recommendation that you do that at about 150k.

Early failures were engine wiring harness and power steering pump leakage. These are very common on this model.

Between 150 and 200k I had the tranny rebuilt, replaced the radiator, water pump as well as the timing chain and rails.

That was a lot, I admit, but the car is still great and I'm confident that it will perform well for the next 100k without anything major.

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02 S500
92 500SL
92 400E (Sold)
87 300E (Sold)
83 300D Turbo (Sold)
75 300D (Sold)
74 240D (Sold after 20 years)