I've owned my W140 since 1996 when she was just 2 years old.
I thought it would be useful to list all the problems I've EVER had with her for the duration of my ownership. If anyone wants specific details on a repair, just ask via a posting. [

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Hope you guys find this useful
Format as follows Problem – Resolution – Who fixed the fault
Rear Headrests not reclining - New switch - DIY
Failed Lumbar Support - Vacuum leak by ZF pump - DIY
Air Con failure - Leak at intake pipe - new intake pipe - Shop
Sunroof Sticking - ongoing - TBA
Rear passenger window sticking - ongoing - TBA
Front door locks sticking - rebuilt front locks twice with new rollers - Removal/fit DIY rebuild Shop
Rear boot lid lock failing - Cleanout and lubricate - DIY
Mirrors not folding - New Switch - Dealer
Rear Centre vents position handles broken - ongoing - TBA
Gear selector light failure - New bulb - DIY
Dashboard lights (fuel gauge/ mileage recorder) - New bulbs - DIY
Dash lights on headlamp on/off cluster - New bulb - DIY
Central lock failure - New ZF Pump - DIY
Water leak - New Water Pump - Shop
Transmission flaring between gears - Transmission Overhaul - Shop
Rear Brake Caliper grinding - New rear caliper + New rear discs (rotors) - DIY
Oil leak at front of Engine - Front gasket of M104 engine - Shop
Squeaking engine drive belt - New belt + tension set - Shop
Drive shaft linkage worn - New linkage fitted - Shop
Ventilation blower motor failure - New motor fitted - Dealer
Ventilation blower squeaking at low speed - ongoing - TBA
Rear speaker buzzing - New rear speakers - DIY
electric aerial stuck down - New aerial - DIY
ABS light on following battery install - Reset ABS light - Dealer
Worn (perished sheathing) ignition leads - New engine wiring harness - Shop
ABS light on following perished ignition leads - Reset ABS light - Shop
Headlamp wiper failure on right lamp - ongoing - TBA
Breakup in lamination on rear glass - ongoing - TBA
Rear screen elements partially working - ongoing -TBA
Centre console roller jammed - forced back into tracks - DIY
Loose Bonnet Star Emblem - New Emblem fitted - DIY
Jump Wiper arm not jumping at screen corners - ongoing - TBA
Pulling to the left - Retracking - shop
Snapped drivers door check-strap (door jam) - New check strap fitted - Dealer
If any more spring to mind I'll update the list
LEGAL STUFF
I'll glady help anyone with problems. I'll describe the repair as I carried it out. All repairs are at your own risk and down to your own competency.