Changing lockshield valve.

[john461]

Hi all. I need some advice. I have just replaced my ch pump as only the upstairs rads would heat up. On the advice of a ch plumber he said after asking me a few questions that he was 99% certain it was my pump.After fitting it I put the heating on and only two of the rads would heat up. The two were upstairs. One nearest the boiler the other the bathroom rad. I told the same ch plumber and he asked if I had balanced the system.Of course I had'nt being a donut .He explained
to me how to do it and I have now got all the rads running ok apart from the bathroom one which is stone cold wheras it was hot before the
balancing.Also this is the only rad which I could not adjust the lockshield.
It was solid and no matter how much I tried to wind the square head down it would not move.In fact I used so much force the square head has sheared off.The advice I am seeking is this. Can I somehow change the lockshield valve without draining the system.I have a open vent tank in loft and the boiler is the back boiler type downstairs.I am also curious as to know why just this one rad would not heat up as did before.Any thoughts would be appreciated.My last question is I have 3 setting on the pump.It is currently on the 3rd setting so should I leave it on that setting.Sorry for the length of this I just did'nt want to leave any info out.I would be grateful for any advice on this, Thank You,,John

 

[nazarineo]

possible airlock ,you could try turning all the other rads off except for that one and see if it forces it through ,then turn the others back on

 

[john461]

Thanks nazarineo. What exactly do you mean by turning off. By turning the lockshields down fully at both ends of rads or just one. Wont this mess up the balancing that I have just done? I have already turned the thermostatic ones down to zero and the bathroom one fully on but it made no difference.

 

[craig51]

just the trvs! Will force water to the last rad.

As for chaning the lockshield, you could bung the system if you know how, this would then mitigate the need for a drain down.

 

[john461]

just the trvs! Will force water to the last rad.

As for chaning the lockshield, you could bung the system if you know how, this would then mitigate the need for a drain down.

Yes tried turning all trvs off bar the bathroom rad one but still no joy.
What I cannot understand is why the bathroom rad was one of the only two that was working prior to bleeding and now its the onle one that does'nt heat at all.
Bunging. Is that where you use a carrot potato or a cork or even a packet of blue tack moulded into a ball to block the vent. not sure what the other thing you block tho.Do these things work?

 

[bengasman]

The question is: why not just drain the system?

 

[john461]

The question is: why not just drain the system?

Well firstly when I drained it before I connected a hose pipe to the rad which is in our hallway 3 metres from our front door.I opened the bleed valves and even though the upstairs rads drained ok two of the downstairs ones did'nt so it was a long job to drain them manualy.
I dont really want to go through that long process again only as a last resort. Secondly bengas man I have just spent £25 on adding an inhibitor to the header tank when I refilled the system.

 

[john461]

Any replies from all you ch experts?