bleeding radiator !!

We have had a radiator that requires bleeding every day for about 2-3 seconds. If it is left say over the weekend then it is considerably longer and will also go to the rad to the bedroom right of it. Up to now i have tried sludge remover, complete drain down and flush out, boiler silencer and new pump. Another issue whether related to this problem is CH will not work unless hot water and central heating are both on at the programmer. My initial thought is leak and to use leak sealer but lately heating not been on, so no pump running all is fine. Would that indicate no leak ? Hope someone can help please.

sounds as if the pump is drawing air into the system which is causing the build up, you need to try to eliminate the source, it may be from the packing glands at the rad valves, although not leaking they might be allowing air in so go round and take off all the rad valve covers and tighten up the packing gland nut (where the spindle goes into the valve) a nip up is fine dont overdo it, it may also be caused by the pump position drawing air down into the system due to positioning etc but start with the valves and see how you get on

Hi, Im not a plumber but bleeding radiators means air is getting into the system.
You would expect to be losing boiler pressure unless you have a feed and expansion tank supplying it. Fresh water also contains air which will require bleeding off, but only in tiny quantities. So if you have a leak, which is then topped up with fresh water, you may well have a constant bleeding issue. Youve got to find out if there is a leak, and also check the feed and expansion system is working properly.
I think air can get into systems via old valves, old soldered fittings and old compression fittings, without leaking a great deal. Its difficult to prove, but Ive got a similar problem, and I think a connection under the floor (in a channel in the screed) is to blame. I will one day get to check it out.
Hope this is some help.

First things first, check the header tank if you have one. If its filling constantly you want to know where the water is going. Maybe its empty because the ball valve is jammed. Does hot water pour out of the vent pipe when the pump runs - or stops? Thats bad. Any one of these things can cause your bleeding problem.

Another issue whether related to this problem is CH will not work unless hot water and central heating are both on at the programmer.

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Some systems are designed that way. Could you ever get CH on its own? If it used to work, I would look for a faulty switch in a three port valve - if you have one.