ok... maybe its the wrong term... but the little screw valve on the front left of the valve cover. (as per last post... apparently its on top of the water pump.
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...to the left of the oil cap. There is a little vertical black cylinder with a hexnut on top. With the car running, you use a small socket (7mm?) to open it, until coolant leaks out. At the beginning a bunch of air will come out, then bubbles, then just coolant. When its just coolant, tighten it back down, then shut the car off.