So I was looking at my cooling system and put my aux water pump back on after I had it off for some years, but after looking at how it is supposed to be installed, it doesn't make sense. The hose connecting the aux wp to the coolant pipe going to the belt driven water pump shows that the coolant flows from the aux wp to the pipe. However, the other hose from the aux wp goes to the hose leading to the heater valve and heater core. So shouldn't the aux wp be pumping the coolant towards the heater core? I assume it should flow that way because the heater valve is there to block the flow of coolant when no heat is needed. I bench tested the aux wp and the water flow is indeed going in the direction of the belt driven wp and there is even a small arrow stamped on it that shows which direction it flows. Anyone have any intellect on this or am I missing something? This isn't the first I've noticed that there seems to be a mistake or fault with the MB design. The EGR valve with the check valve is another that has always baffled me, but no one seems to be able to explain that either. Hmmmm

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1990 190E 3.0L