All Things Wear
Brother of The Benz 450 SLC 5.0,
If the proper concentration of coolant and water has been maintained, I don't believe the impellar would wear enough to be measured.
The temperatures you are experiencing are quite acceptable considerring the cooling system is pressurized to at least 13 psi.
The pressurized system has a higher boiling point as does the coolant mixture.
The higher the engine coolant can run the better it is for your engine. The engine lubricant is cleaned better in the filtration unit and any condensed fluids in the crankcase are evaporated at these higher temperatures.
I'll take an engine running at 85-90 or even 100 C. over one at a less temperature. After all 100 C is only 212 F.
You may be able to see the circulation of the coolant in the upper tank.
Keep maintaining the proper mixture of coolant for you have already done your preventative service and watch for any radical temperature changes.
All prudent Benz owners do this as routine instrument scanning.
Happy Trails Beep Beep from The Spiderman in Houston!!!