I have been watching the coolant level and adding until the level stabilized.

I suppose if there is ever a time to "worry" it is when putting a new engine into service. Objectively, the cooling system in the car is perfect, and an 80deg thermostat should operate at 80deg. I do have a lot of money and time tied up here, so I would like to understand and protect the investment. I'm still acclimating to the car, and if it is consistant at 90, so be it.

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Chief

1991 350SD

That would be an incorrect conclusion. The figure of "80" indicates that this temperature is the point where the 'stat just begins to open. In reality, depending on many other variables, the system will operate between 80C.and 94C. At the point of 94C., the 'stat is fully open and the cooling system is operating at it's maximum capacity. Of course, as the coolant temperature climbs above 94C., the capacity is also increased, so it's a bit self-regulating once the 'stat is not in equation.

The purpose of the thermostat is to "enforce" a minimum temperature. Considering that an 80 degree thermostat only begins to open at 80 degrees, and does not fully open until 94 degrees, the expectation of an 80 degree operating temperature is completely unreasonable.

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

Good information, useful to think of the thermostat operation that way.

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Chief

1991 350SD