The thing that's unique about the monovalve (whether combined with the pump or not) is that it's "SPDT" (if it were an electrical switch). There is always a path for hot coolant from the rear of the head to the thermostat housing. Depending on the position of the monovalve, the coolant goes through or bypasses the heater core but the flow is always there. I assume Mercedes did this for temperature control, to "improve" smogging. In any case, it appears to be unique. Other Mercedes diesels (and some gassers) have no coolant flow from the rear of the head when the heater is off. Weird, huh?

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970