I have a similar problem which I recently posted three days ago. Yesterday, I changed the oil filter element along with the included two o ring gaskets. I then bled/purge the air until i see a clear oil flow and thereafter close the bleed valve and the boiler fires up. Although I constantly have to manually purge out the air in order to start the boiler, i noticed the time it takes is much shorter than before. Previously it took anywhere between 40 seconds to 1 minute and a half to purge the air out. this time , it took an average of 5-12 seconds to have a clear oil flow then i close the bleed valve and she fires up.I BELIEVE THIS TELLS ME THE AIR IS GETTING IN BETWEEN THE OIL FILTER CASING AND TO THE BLEED VALVE. I SUGGEST YOU MAKE SURE THE TOP BOLT ON THE OIL FILTER CASING IS FIRMLY TIGHT AND THE BLEED VALVE AS WELL. A FRIEND MENTIONED, A SLIGHTEST OPENING CAN CAUSE AIR TO SEEP IN THE SYSTEN AND CAUSE THE AIR LOCK OUT. Unfortunately for me, the problem persist, however it did reduced the purge air out process in half the time. This tells me my connections were not tight enough causing air to get into the system. Good Luck
AUSTRIA, November 2012