Mercedes-Benz W140 thermostat and too low operating temperature
300 SE400 SEL
What is the normal operating temperature of the W140 and when is it too low?
A warm engine that has been driven over 10 km runs at about 80 degrees or more. If the temperature stays clearly below 70 degrees even in winter, the thermostat is probably broken.
Why does the W140 temperature not rise?
The thermostat can stick open, so the coolant circulates constantly and the engine does not warm up. If the thermostat is several years old, replacing it is worthwhile.
Which thermostat is fitted to a W140 M119?
The thermostat is at the end of the upper coolant hose between the cylinder heads, and both versions are 80-degree. There are two thermostat versions, and the right one is chosen by the engine's serial number (part 17 or 18). The gasket is replaced at the same time.
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