I replaced the thermostat on my OM606.1 about 10K mile ago. Lately it has not been opening until about 90-95C. I confirmed this with a thermocouple thermometer while heating the thermostat in water. The water temp gage hangs a little over 90C on cool days and up to 100C on hot days. When the thermostat was new, it was slightly over 80C. Will running at this higher temperature cause any issues? From what I have read on the forum, the only time to be concerned is when the water temp needle get up to the 120C position. Is this true?

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95 E300 Diesel 200K

Not in normal operation, and as long as your aux fans work. At least in the older diesels, the typical temperature is 87*C for the thermostat but Behrs have a reputation for running hot (if that was your replacement). Honestly, if it bothers you I would just go ahead and replace the tstat again, it isn't expensive.

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TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth