Outstanding write-up! It has been some years since I have replaced a W123 starter and this thread is a great refresher for me.

One observation I'll offer:
Where there is discussion in the thread to "Rotate engine clockwise by means of 27mm socket attached to crankshaft bolt at front of engine...", I would add:
First, place your vehicle's transmission shifter into the "N" position.

Thanks for this great DIY post.

you're welcome - im glad it helped you out! i'll make that change :-)

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Sure glad members post such great information, I had starter go out and in two hours with the help of this post- a starting benz in my driveway. Thanks for the great forum!

Thanks for all the helpful advice

I was anticipating a lot more trouble, but once I gave myself a few good kicks and got started the job ran itself

Soaking in PB blaster for a few days worked wonders as both bolts broke without the need for breaker bars.

(other things on this vehicle were a real bear to undo)

Top bolt I used a 1/2" extender and home made allen socket made from 10mm socket and allen key from local pawnbroker. Used my regular cheapo articulating section just behind socket.

Bottom bolt I used a 3.8" driver which fitted the space more easily, with a small 5" pipe extender and pulled by hand. Couldn't believe it.

Turning the wheels all the way to the right was just what the doctor ordered. I felt they designed the steering setup exactly for the starter to pass through.

Putting new starter back on was unbelievably easy. I pushed it up into position and it stayed put! I loosely tightened the 4 bracket bolts so I could wiggle the starter until both big bolts bit.

This was a joy to do and I look forward to doing my daughter's 84 sedan starter once I have the old one rebuilt.