Performed a heating pm on an oil boiler. Brushed and vacuumed. Replaced the oil filter, nozzle and strainer. Started and checked the safeties. Performed a combustion test. 3.4% o2, 28 ppm, 85.5% efficient System is operating properly. The upstream bedroom zone is heating due to the flowcheck inside the circulator is not closing fully allowing some water to go through the zone when it is not calling. Recommend replacing the circulator and Hi-vent on the air scoop. We will have the office schedule the replacement.