Dan, yes the system has a thermostat! But it is a pain to replace as you must remove the oil filter housing.
The thermostat should start opening at 92C.
The part number is 117-180-01-75 and lists for $27.
Check Fastlane!! You will also need a new gasket # 102-184-09-80.
MERCEDES Benz Master Guild Technician (6 TIMES)
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