I have two radiators in my house that are only hot on the top half (not the bottom). i was told that they needing bleeding, which I did. this has made a difference to the one's that weren't as hot as they should be but not the ones i have the real problem with.
i had a new condensing boiler fitted about a yr ago but decided not to have the radiators changed so they old'ish.
paula1979
September 2007
Don't listen to Brian, it's quite obvious he knows nothing about central heating. Air would make them cold at the top. If radiators are piping hot at the top but stone cold at the bottom it due to sludge build up in the radiators. A power flush would sort the whole system out, but if its only two rads turn them off both ends, drain them and take them out into the garden and give the a good flush through with the hose. Give then a good tap on the back with a rubber mallet to help loosen the dirt. Then reassemble and bleed. - job done!
the gas man
September 2007
If rads are hot at the top but not at the bottom there is an air lock normally cleared by bleeding the rads, try putting the pump on to circlate the water and rebleed. I this fails you may need to back flush the system:
Tie off the tank ball valve and empty some water out, find the drain cock to the system (normally near the fire) connect a hose from a cold tap to this valve, open the valve and turn the tap on. DO NOT overflow the main tank.
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