i am going batty. i have a boiler that has three zones. basement, main floor and 2nd floor. my problem is with the 2nd floor zone. i have a lot of banging and water flow sounds when the thermostat calls for heat. i have spent two plus weeks bleeding air out of the pipes--doing this by the bleeding valves on the baseboard units. after all that bleeding the pipes still cause quite a racket and when i bleed at the last baseboard unit in that zone i am CONSTANTLY removing more and more air--WHERE is it coming from--why can i not get all the air out--it seems like air keeps getting in the pipes--how?? what do i do?? this is such an unresolved problem.
Are you sure you are bleeding air out as opposed to the system's sucking air back in? Verify that you have some pressure in the system and the expansion tank is not full of water. Quick preliminary calibration of expansion tank: empty it of water, then repressurize the system to specifications.
The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.