89 560sel. I hear 85C is normal operating temp. Some say OK for temp of 110C. Some say no. I hear Elec. AUX Fan kicks in at 110-115C. I AM CONFUSED. My car runs at 85C. If air temp over 90F- eng. at 90C-95C. If air cond. on above 90F +60mph - guage goes to 110C - turn air conditioning off to avoid an overheat condition. I have seen the damage to an overheated mercedes v-8 where a piston exploded a short while after the overheat - mechanic says the metal properties changed from the overheat. PLEASE - WHAT IS THE HIGHEST TEMP. a 5.6l CAN OPERATE AT WITHOUT ANY WORRY OF DAMAGE TO ENGINE? Is 110C NORMAL on a hot day? What temp. SHOULD NOT be reached to prevent damage? If engine runs hotter-why 85C thermostat? FYI - changed hoses, pressure cap, thermostat, cleaned rad out of car, new water pump & installed new centrifical fan clutch, using genuine Mercedes parts. Temp. still goes to 110C on days over 90F with air cond on, don't know if it goes higher because I turn air off to avoid engine damage. If I short wires from the temp. switch together, the aux fan runs constantly & temp. never goes up over 100C. When the guage reads 110C - the aux fan still does not kick in. Again-- WHAT'S NORMAL??