because the stock thermostat also acts as a valve. When it's closed, it will allow coolant to go only into the coolant bypass. When it's open, it closes the coolant bypass and allows coolant to go into the radiator. When you take the thermostat out, you take out the valve...therefore the coolant bypass is ALWAYS open....so some of the coolant may go into the radiator...but most of it will just hit the bypass

 

I wonderd who else was doing this. Tap wayer is high in calcium and metals and clogs your radiater like the office coffe pot. Good advice.