At our shop, not only do we repair & service benzes,,,,but we sell them also. It has gotton to the point that we completely avoid the cars with the 104 engine! It's very simple,,,we can not afford to sell these cars and stay in business. I have had well maintained, nice cars, (just out of factory warranty) spew head gaskets,engine comp wiring harness die for no reason,etc,etc.
We get alot of cars direct from MBZ credit corporation (star car program), and they recently revised their "arbitration list" to not include any head gasket failures. In other words,,, so many of the stinkin things are pouring, that if you are unluicky enough to have bought one,,,it's your baby!
There is a large dealership about 70 miles east of me, who has a budget "set aside" and a tech who does replace the gaskets on a "goodwill" status, depending on miles etc.
The other big problem I have seen is with the wiringharness in the engine compartment. They just totally disentagrate inside the plastic shrouding and start to short out.
I've been working on benzes for almost 20 years now, and (alot of experienced MB techs will admit "in private") that the 104 didn't measure up to the quality standards we have all come to expect.
Disagree with me, be mad, whatever(I'm not trying to tick anyone off),,,,,I'm just being totally honest with you all as to my experiences (and two local dealers) with this series engine.