I have a Crane gas boiler for our hot water baseboard 2 zone heating system. I drained the boiler enough so that I could replace the circulator motor. After filling the boiler via the auto fill valve and running the system, it certainly sounds like there is gurgling air in the system. I tried bleeding the baseboards where there were air valves. There are 2 valves with hose connections teed off the return line. One is before zone valve 2 and the other is where both zone valve returns meet before heading into the circulator pump. Could they be used to bleed out the air? Thanks
You seem to be describing purge and balance valves which are used for the purpose of purging air from the system after making repairs.
Note and mark one side of the balancing valve position with a magic marker so you can return the balancing valve to the same position as before. Turn the balancing valve to block the flow of water. The slot or indicator should be across the tube to block the flow of water. Then open the drain to let water and air flow out of the lines. Close them when the lines run clear. Return the balancing valves to their marked previous positions.
The removal of air can be improved through proper piping, location of an air scoop and circulator, and air vents. Visit: http://www.hydronic.net to look at the design instructions and pipe arrangements to see if anything in your system can be improved.