Funola is right. In fact the monovalve depends on the light vacuum from the aux pump in order to function properly. Sad to see mis-information persist for sooo many years

A WVO (or other additional) coolant loop should be sourced by being teed into the coolant outlet near the oil filter, and returned by being teed into the discharge side of the aux pump between the aux pump and the engine block. To prevent the coolant from flowing backward in the WVO loop it needs to have its own transfer pump located anywhere convenient. This loop will have an outsize affect on cooling the engine since OEM coolant flow through the head is not that great... which is why turning on your heater in hot weather instantly cools the engine down.