Coolant bleeder is always up and venting
 

My coolant reservoir bleeder valve is in the up position. It can be pushes down but springs back up. I'm guessing that the whole thing needs to be replaced, could it just be the o-ring?

It goes up and down with temp. Dead cold it should be closed but as the car warms it will pop up. If it doesn't work this way, I would change the seals. Be careful, the screws that hold the valve together thread into soft plastic. Its very easy to strip the plastic threads and/or break the screws.