Hi all,

A Merc will NOT overheat unless there is something wrong with the system. I live in the tropics and have had similar problems. In fact it was dealer induced. The water pump failed and after they replaced it (before this it was always steady at just under 90C) the temp soared almost up to 120C--- Not funny. I took the radiator apart and cleaned it - no difference. I finally decided to take the thermostat out and check it in a saucepan BUT the dealer had removed the working parts of the thermostat without telling me!!!! Got a new thermostat and PERFECT! Back to normal. DO NOT EVEN THINK OF REMOVING THE THERMOSTAT !!! It is needed to do the job.

It sounds to me more like a water pump problem - I would check that first and then go on to the thermostat. After that flush and clean the radiator.
Mine is not overheating at all now in spite of the fan clutch not working properly (I can actually stop the fan with my finger even when at operating temp). (BTW Don't try this unless you know what you are doing...)
Other things that cause extra heat is late ignition timing but then you would also experience sluggish performance.

Good luck with it!!

Tom

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'90 300TE 4-Matic