Cleaned and checked gas boiler. Inspected and cleaned heat exchanger. Checked flu piping and draft. Cleaned burners, pilot, and flame sensor. Checked voltage and amp draw of pump. Filled system. Bleed air from system. Found high expansion rate. 6.5:1. Expansion tank is too full. Suggestions: replaced thermostat batteries. Drain expansion tank: $100-$300 if serviceable. depending on fittings/piping coming loose for service and amount of draining system requires. If new expansion tank is required, could cost: $1000.