Yes welcome etsa, this is a great place to learn about your new purchase. I too have an 87 260E and can only give you my experience, as I am not mechanically inclined.
First, this is my daily driver with the original engine and tranny with over 285,000 miles. Still strong and silky smooth, so your car has a lot of life left...enjoy!
The headrests may need some extra vacuum power. When driving, get your speed up a little, you can do this safely at 25-30mph, and then let up on the accelerator pedal, while at the same time hitting your headrest button. This works on mine when they are stubborn without fail. A car this age sometimes loses vacuum and just needs a little help.
The pinging might be an indicator for a valve job, or stuck lifter. Mine is starting to do this, with my mileage it is bound to happen. The engine is still very strong, as is the tranny, but it will need another valve job at some point, and the lifter fixed. I believe the "general" concensus is the valves start to go about 100-150,000 miles. I currently have 160,000 on this vavle job, and oil usage is increasing.
What is your cars oil consumption per 1,000 miles? Or, how many miles do you get per 1 quart of consumption. I believe MB standards indicates normal is 800 miles and above per 1 quart of consumption.
The heating problem could simply be the need for a good flush, fresh coolant and new thermostat. If you've done that, then I'm not sure. I can tell you when my radiator cracked, slightly, I replaced it and it ran about 10 degrees cooler, never have used Water Wetter. Sounds as though yours is running more than 10 degrees above normal though.
Hope this helps some, and again, welcome to a great site, with first class people. This is a gold mine of info!
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