The original valve was leaking so I took it out and replaced it under the hood with a manual open/close valve.  The problem I have is that when I close that valve water still circulates through the other heater hose to the heater core and I sill get heat in the car. What I am wondering is will I have to use a 4 connection valve that has a by-pass or can I close off both heater hoses without any problems?