noise from expansion tank

hello all. i have a single zone hot water heating system with an external coil. the circulator is continuously run for domestic hot water. it appears that air may be getting in the system. i had a "heating prof" in and he filled sysem and bled it from a valve located near the boiler. i live on the first floor and the heating pipes run from boiler, overhead, and then down to baseboard radiators. when he first filled and bled the radiators i heard nothing from radiators or boiler. the next day i heard some bubbling noise from the radiators when the mech zone valve opened. the noise became progressively worse each day. i have since bled the system again, and the radiators are much quieter. however, i now hear a gurgling/bubbling sound from the expansion tank each time the burner comes on. the burner comes on at 170/180 and goes off at 200 degrees. could the expansion tank be faulty and somehow letting air into sysem? i believe the expansion tank is one of the newer ones with a bladder. thanks for any help.email me at snipped-for-privacy@verizon.net just remove the 5 for spam purposes. or post message with any help. thanks again.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.