im curious as to why the BAC valve needs to be hot. the coolant hose runs beside it, not through it. anyone know?

 

It doesn't need the coolant lines attached to perform properly. It is just a convenient place to "hang" the coolant lines.

 

Actually, the coolant flows through the BAC to prevent it from freezing up in the winter. In the winter, the BAC is flowing cold air. If there's any moisture, it can freeze the valve and cause it to stick. Many idle motors have a coolant feed for this purpose.