Temp runs between approximately 85-95 degrees c at highway speeds. Immediately rises after exiting highway speeds, and will boil over if continue stop and go driving. I have replace thermostat and poly belt, flushed. Solution?
Bad water pump, bad electric fan motor(s), bad coolant temperature sensor, radiator cap, cooling fan fuse or a blown head gasket. If your Mercedes has a belt driven fan forget the stuff about motors and fuses, it could be a bad fan clutch.
Thanks–water pump seems ok, fans come on at right tempature, sensors ok, fuse ok, doesn’t seem to be gasket-no white smoke, no missing and has not worsened in driving over 3000 mi. Is there nany way to test fan clutch?
You did not tell us how old your Mercedes is, but it is possible that the radiator is partly blocked.
However I would tend to go along with Xebadaih’s list, just adding mine suggestion on at the end. Start checking things out at the top of the list.
Do let us know what year and how about the miles as well.
My informal poll says that questions about Mercedes vehicles recieve only general type responses,it doesn’t seem we have a Mercedes expert (Ok Benzman is one) on board.
I stopped working on Mercedes when I could not keep from banging my head on the grill.
I am heavy into BMW and Chevrolet,couple of old Dealer mechanics are masters at SAAB and Subaru,everyone knows something about FORDS and we have a couple of top men on transmissions but no one about Mercedes.
A year would be helpful in getting more specific, since Mercedes has made the S class since the 50’s.
1992 SEL with 126K