I've been having the same issue with my car for awhile too. It hasn't done it in quite some time, but removing the bubbles helps, and draining your old coolant and adding some 50/50. If this has been going on for a long time like you stated, you might have a blown headgasket.

Of course, this is what pro's have told me. But then again, I don't drive a Honda.

Im also getting a new radiator cap for my car, soon.