Hello everyone
I'm new to this forum but have read hundreds of posts
and an sure someone can point me in the right direction.
My 88 300ce was running in a normal temperature range
one day and running right up to the red line the next.
Checked all the usual items(belt coolant oil etc)
Now at speed the temp is a little higher then before
and as soon as I slow down the car heats right up.
Even with the electric fan on the temperature will not come down,
Radiator replaced w/oem a few years ago (upper neck issue)Thermostat could be original.
Car still runs well with no loss of coolant at all.
I did notice that at idle I was able to(CAREFULLY) stop the fan from turning very easily.
Any ideas?
Thanks JIMMY

Change your thermostat.

Most likely your viscous fan clutch is worn.
The new upgraded ones only fit with a new fan and pulley, check before you buy it.
There are treads on this forum about refilling the clutch with silicone, never tried this myself.

First check if your radiator gets hot, if not the thermostat is bad. The clutch gets its heat from the radiator. If the radiator not get water from the engine the clutch will not engage.

Rob

Also check the aux. fan whither it is working or not. And check for air in the coolant watercourse.

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380SE 1984 <------- Totaled by flipping accident
300SE 1988 <------- Sold
Volvo S70 2000 <---- 4 family
Opel Omega 2002 <-- 4 family
560SEC 1989 <------ Sold
560SEL 1990 <------ Sold
560SEL 1991 <------ 4 my mother
560SEL 1989 <------ Sold
600SEL 1992 <------ Current

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Replaced thermostat today with oem part from the local dealer.
Twenty-two dollars and twenty minutes later the temperature is right in the center and stays there.
An autopsy of the old t-stat(date stamped 8-87!)revealed the main valve locked up so tight that I broke it trying to move it.

Thanks to YAL ROB-PRUIJT & ZCC