Hi all, was wondering if anyone had any idea what could be wrong with my sisters heating. She has a Baxi Solo boiler, the upstairs radiators keep getting air in them, downstairs seems ok. I air them and get the radiator warm then when the boiler gets turned on it just seems to empty and need aired again. I did notice that the hot water seems to fill up in the header tank. I very much doubt there is a leak as I have checked the manifolds and from there its 10mm pipe so there is no joins and the route it takes I would definitely see water, especially as it is 4 radiators worth of water. After airing and getting the radiators warm, one of them is exeptionally hot even when boiler is turned to very low setting, not sure if this is relevant. I'm not a plumber (spark) but would like to try to sort this, or atleast know a probable cause. The hot water side of things, including immerser are ok too. Thanks.