On my sailboat, the bypass cooling system allows the waterpump to circulate water without passing thru the engine block until the engine gets up to temperature. At that point, the thermostat opens and blocks the loop that bypasses the block, forcing the coolant to circulate thru the block.

I'd be curious to see a diagram of the operations of an MB cooling system since it is not clear to me exactly what is happening.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13