I've searched through the forums and seen where people have made mention of "pulling out" the drain petcock to replace an o-ring when they've went bad. My question is one of clarification. Are you pulling it out till it's exposed and replacing (or in my case putting one where there wasn't) the o-ring or are you actually pulling it all the way out of the radiator and getting to an area that isn't visible in the pic? Where exactly should the o-ring be?

 

keep twisting and valve will come out completely from radiator.