Running at the mark between 80C and the red zone is normal in heavy traffic, sitting with the AC on. Otherwise, you shouldn't get that hot.
What have you replaced in the cooling system?
Coolant tank cap? These do go bad and will cuase overheating since the coolant will boil at about 120C.
Radiator -- aluminum, they only last so long, and tend to fill up with corrosion, limiting cooling capacity. It's worst in a circle that matches the fan.
Bad radiator hoses -- lower one can collapse under load, reducing coolant flow.
Bad thermostat (very common), won't open or close fully, so you run hot when it's warm out, cold when it's not.
And so forth.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!