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. System is operating properly. The domestic water coil has a lot of corrosion around one fitting and on the coil plate. Recommend replacing the domestic water coil. There is also corrosion on a hi-vent showing that there was a leak. Recommend replacing. The boiler is a steel boiler and getting up there in age. Recommend replacing in the future.