Top floor rads won't bleed properly

[hardm2000]

HI all my first post so i'll try to include everything, first off the ch system is a gloworm ultimate open system. The problem is that the top floor rads will not bleed fully, when i try air comes out but will not get to the water stage. I'm doing this with the heating off and if i trun the heating back on for a while then off to bleed again there is more pressure to bleed the air out but never reaches the water stage again.
We had the bathroom done about two years ago and the system was probably drained and i know for a fact the plumber did'nt re add inhibitor which it has had from new now 12 years old.
I recently added inhibitor and noise reducer from sentinel which made the boiler noise quiten down for a bit but still had the prob with the rads. I am know getting loud noise from the cylinder upstairs under the f & e tank in the loft, the noise i can only describe as what i think is maybe an element boiling dry??

From what i have read elsewhere i think the f & e outlet may be blocked as it does'nt drain when the rads are bled but this is all guesswork as i know nothing of ch, if this is the case how do i go about rectifying it?

Sorry for such a long post but im trying to include evrything i can, also if anyone needs to hear the noise i can upload it for someone to listen to.
Many Thanks

Ben

 

[seco services]

the rad problem does sound like a blocked cold feed or empty f/e tank.

you sure the noise is from cylinder and not the pump running dry ?
as for the cylinder do you use the immersion element in it if it has one fitted.?

 

[hardm2000]

No ive never used the immersion element that i know of there is a switch by the cylinder which has always remained off, i'm pretty sure the noise is from the cylinder not the pump but will check again in a min.

 

[hardm2000]

The sound that ive just heard now does sound like its from the cylinder but maybe the pump struggling for water??
Not sure at all if the F & E outlet is blocked how do i go about sorting it?
Noise can be downloaded from here
http://rapidshare.com/files/192628587/ch_noise.m4a

 

[seco services]

if you can open the lowest draincock on the system and drain some water see if the tank emptys and the ballvalve opens to let water into the tank

 

[swidders]

Not always easy to resolve blockage but you could first trying blocking the overflow/expansion pipe (the one that goes in from the top) with a speedfit endcap, drain the system down and force mains water through the feed outlet at the bottom of the tank, leaving the drain plug open. Or vice versa - connect hose to drain plug and force water back through the system into the feed outlet.

 

[hardm2000]

Not always easy to resolve blockage but you could first trying blocking the overflow/expansion pipe (the one that goes in from the top) with a speedfit endcap, drain the system down and force mains water through the feed outlet at the bottom of the tank, leaving the drain plug open. Or vice versa - connect hose to drain plug and force water back through the system into the feed outlet.

Ok if im going to drain the system down how do i empty the f & e if its blocked and also whats a draincock and where would i find it?
Thanks

 

[swidders]

Draincock is likely to look like a hose connector and should be on one of the radiators on the ground floor, or somewhere on the pipework at the lowest point in the house. http://www.screwfix.com/prods/11074...lves/Radiator-Valve-With-Drain-Off-15mm-x-1-2

See what water comes out and try connecting a hose to the mains with the overflow at the FE tank plugged. If you're lucky, this backflow will shift some gunge. You can leave this running for a while an rely on the tank overflow to run the water reasonable clear down the side of the house or wherever it is situated.

On the other hand, to empty the FE tank if it's blocked and you want to try the hose from this point, a bucket and sacuepan will do the trick.

 

[hardm2000]

Thanks for all the replies i will let you know how i get on.