unable to drain down central heating system

[Jilly]

please help, my mums boiler a Solo Baxi 2 PF, started making noisy a couple of months ago (werent to bad , then seemed to stop). The radiators were all ok. Today she called me saying all some of the 3 upstairs radiators were cool in places, one almost completely cold. Also 2 of the downstairs rads were cold on top warm on the bottom. Previously when this has happened, I have bleed the radiators, heard air hiss out with water and then the system has settled down and has worked ok. however, today when I attempted this the 1st radiator did as above air hiss and water when doing the 2nd rad again the same but at the same time a violent baging and thumping noise from the pipes directly above the boiler. After switching off the boiler, I tried the upstairs rads, no air or water came out at all. Switched the system back on all the lights came on as usual but after about 1 minute the pilot light, and fan light went off, and again loud banging from the pipes directly above the boiler. Sounded like a very bad air blockage. Then tried to drain down the system no water came out at all. Then tried to open up the bleed valves starting from the top of the house working downwards slowly in case a vacum had formed to try and relieve break it so that water would drain out. Still no joy, any suggestions or do I really need a plumber in. Forever, grateful for any assistance. PS. the system is only 5 years old and has been treated in the past for sluge etc.
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Moderator

edited to add

Doitall, thanks but also forgot to mention ballvalve working ok, as mentioned no water coming out of upstairs rads and water wont drain out of downstairs rads (and I know theres water in there) so whys it not draining out. any other suggestions welcome

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Moderator

Please do not start another thread for same subject, please reply to your replies ( i have removed your other post of same name)

 

[doitall]

could be a blocked cold feed.to test you need to drain some water out the rads and see fi the header tank starts to fill, check ball valve is not stuck as well.