A customer in an older Alexander home reported that their upstairs radiators were cold while the downstairs ones were hot, accompanied by a gurgling sound from the boiler. I identified the issue as air trapped in the hydronic system, which was preventing proper water circulation. To resolve this, I performed a full system bleed on all radiators to purge the trapped air and then repressurized the boiler system to the correct level. The customer is delighted that all the radiators are now heating up evenly and the strange gurgling noise is completely gone.