No heat from radiator

[Steven Campbell]

I have an ancient central heating system which is open. My bedroom radiator has no heat from it at all yet the one just through the wall is roasting. If I bleed my heater the water coming out eventually gets hot while the radiator itself becomes lukewarm. Once the heating is switched off and back on again, the radiator goes back to the way it was before with no heat.

Something similar happened a few months back when I had to disconnect my bathroom heater. I tried doing the above steps of running the water through it but it would just return to being cold each time the system came on. Then strangely it came back to life of its own accord a few weeks after I had tried this.

Since I have reconnected the bathroom heater (4 weeks ago) I am back to square one with no heat. I thought maybe the heater would have come back to life again but no such luck.

Is it worthwhile me continuing to bleed it until the hot water runs through it to see if it clears the problem or do I finally need a new radiator?

Cheers

[Dark Angel]

Silly question, but have you checked to make sure the return valve is open?

[Steven Campbell]

The heaters are that old I can't budge the knob!

I would have thought if the valve was closed or there was a blockage then I wouldn't be able to remove so much water from them. I must have removed at least 2 basinfuls.

Steven.

[Dark Angel]

There should be 2 valves on the radiator, one on the inlet and the other on the outlet. If either valve is closed or blocked you'll still be able to bleed hot water through the other when you open the air-pip.

[Owain]

For the radiator to get hot, both valves must be open, so the water can flow IN and OUT through the rad.

For you to bleed it only one valve needs to be open (and it doesn't matter which) so water can flow IN to the rad.

Owain

[Set Square]

So, to follow on from that . .

Bleed it with one valve open and one closed. Then close the first one and open the second one, and bleed it again. Bleed several pints out each time to make sure there are no airlocks in the supply pipes. Finally, open both valves.

[Peter Andrews]

As you say it sprung back into life once before, it's possible that you have an airlock in the pipes feeding that radiator. Try closing the valves on the other radiators with the pump running, this may shift an airlock. Are there any horizontal runs associated with just this rad where air may get caught? I once spent half a day trying to dislodge an airlock on a friends system where the pipe was not quite horizontal. It's unlikely that you need a new rad, albeit that the work in changing it may clear the problem!

Peter

[Ed Sirett]

It seems that google doesn't go back before 2001 at least for uk.d-i-y

A number of year ago I wrote something like:

Bleeding radiators is not the central heating equivalent of 17th Century medical practice. The bleed valve exists for the purpose of letting air out or in.

Sometime a radiator does not get hot because it is full of air (however this is often the symptom of a bigger problem elsewhere).

I would check that both radiator valves are open especially if one of the them is a TRV which may have stuck fast.

[Steven Campbell]

Thanks guys you have gave me loads to go and try. Like I said, the system is that old I will probably have great difficulty turning the valves open and closed in the other rads as someone suggested. As I know I can't budge this radiators valve. There is a lot of horizontal piping to this radiator and since the heat loss occurred only after I disconnected the bathroom heater, it does make sense that there could be an airlock. Even when the radiator was working properly it was only ever warm in the top half of the rad so if it comes to it and I have to change it then it will be no big loss.

Thanks again.

[Steven Campbell]

Just to update all the helpful replies. My valve had been stuck in the off position. As soon as I got the mole grips out and forced it open the radiator became hotter than its ever been.

The previous occupants must have set the valve to just on and no more. Over the years I don't know if the sludge in the system has maybe blocked the valve and was letting very little hot water in and with me working on another radiator I created even more sludge and blocked it fully.

I just presumed the radiator was that old and that is why the bottom of it was always frozen but not now.

Thanks again.