1983 mercedes 300D w123;
When I bought it, it didn't turn off with the key. Mercedes put a lever under the hood with a big red stop sign for just this occasion. I'd pull in somewhere, take my keys, open that 100 lb hood, and shut it off. I got fuel in new jersey and the 25 year old female full serve attendant saw me under the hood and thought I needed a rag to check my oil. "or something." I think she thought her routine would be interrupted by actually doing something "car-ish". I mended this with a re-wire of the vacuum system.
Its HVAC system has ghosts in the control head, and won't turn on the blower fan until it's been driving a while. Or maybe the fan's brushes are nearly shot. Meh. Summer car.
A spring in the tranny valve body is weak, so it spends half a second in 2nd gear before going up to 3rd. If I tromp on it at just the right time though I get a good pull in 2nd. This gear is important for integrating into traffic. Basically one has to drive it like they stole it.
Steering box is slightly sloppy and none are available.* They say one can use the w126 box with the w123 pitman arm. *MBUSA has the proper box for approx $2200.
Something's gone berzerk in the turn signals and they flash about 300 times a minute. The "hazard module" gets most of the blame online. Car has no cupholders so idiots spill their coffee in the center console where this stuff lives. While my incandescent turn signals maintain a half-on flicker, I figure if I put LEDs in it would strobe like a disco.
I have antique plates for it but my state lets me run "contemporary" 1983 plates on it so long as I keep my real ones to show the fuzz. Got said plates off ebay. They had a 1984 sticker but I peeled it off with a hair-dryer.
On the plus side I adjusted the valves, changed the filters, and it's good for 28.5 to 34 MPG. I got it down south and it has no rust and, in fact, a sun-faded paint patina that you just can't
buy.