Good input from those posting replies. I've only experienced the 'typical" issues with my '92 400E. Check wiring harness. A problem there can create all kinds of strange engine behavior. I personally checked with a local Benz dealer whose service mngr pulled my VIN and was able to see the harness had been replaced. Power Steering pump leaks are common. ALthough a peripheral and not directly an M119 issue, you will experience "the leak". Motor Mounts fail I assume due to the poor airflow inside the crampt engine compartment. Rotors and dist caps get harsh treatment on the 119. Just consider them a mntc item. Oh yeah... a common issue: Belt Tensioner assembly. Seems to be a 60K mile disposable part. Like the mounts, the heat under the hood seems to shorten its life. Other minor items I have experienced are:
Leaking oil psi sending unit
Leaking oil level sending unit
I suppose you could classify all these issues as superficial. Overall, I am amazed at the 119's dependability, durability and power.