a 92 vehicle, I believe you have a W140.

I had the same problem before and it turned out to be a faulty water pump.

The next I had after the pump replacement, I meant many months after the replacement, was the fan clutch. As the car ages, the clutch ages and had to be replaced to restore the effeciency of the clutch operated fan.

Other things you should also consider:

1) your thermostat. Has it been replaced last time you flush the system?
2) Your aux. fan. Are they working when the car reaches 100C? or intermetly when the air/con is turned on?
3) Is you collant the right mix?

Perhalps you should describe a bit more about your problem, i.e. time vs temperature rise before we can say anything. Any one of the above or all of the above affect the cooling system.

cheers