One boiling hot radiator, the rest suddenly stone cold!

Hi, this evening came home to my flat to find my radiator nearest the boiler (and the higher one) boiling hot, yet all others freezing cold. Having read the advice here, we have managed to 'push' the heat to the farthest radiator, by turning each one off in turn.

However, once the farthest one was hot, I reopened the valve on the radiator nearest to the boiler only to find that the original problem returned. I.e. the farthest rad went cold and the initial hot one just got hot again.

Any ideas? We have a combi boiler that's approx 10 years old and have recently bled all our radiators and this is the first trouble that we've had in 4 years. As we're in the middle of the cold snap, any advice would be gratefully rec'd, thanks!

did you top the pressure back up? look for your filling loop and bring the prssure to 1 bar when all the rads are cold.

Hi, thanks for getting back so quickly. Yes, we had that disaster last week and have since refilled back up to 1 bar pressure! Another quick check has shown that the 2 radiators nearest the boiler are now red hot, but the remaining 3 (small 1 bed flat) are still cold.

I'm going to continue to experiment with the idea of 'pushing' the heat around the system, but if there's anything obvious that we're missing, please feel free to let us know.

Also, the boiler can only be turned off at the wall now as despite it being on timer and supposed to being off, it is continuously firing up for approx 5 seconds and then shutting down. Any advice would be gratefully appreciated as we can feel a big British Gas bill coming on!

The rads nearest the boiler only need to be opened half a turn or so, if you open these fully then the water will take the easiest route back to the boiler. Try and pull in the hot rads until the flow diverts to the others.

In other words: Try Balancing the system

Thanks Dave. At the risk of sounding really stupid, do you mean the thermostat valves should be only half open or the valve on the other side (without numbers)?

the lock sheild valves ie not trv's

Thanks, will give it a whirl now. Still don't understand why after 4 years with no problems, this would suddenly happen overnight and the whole system need rebalancing. Also, doesn't explain why the bolier is constantly firing up for 4 seconds, then switching off for 20 seconds. My husband thinks that the pump is gone, would that seem right to you? We also recently bled all the radiators and topped up the pressure, could that have had an effect?

Boiler cycling would indicate an airlock, pump damage or a blockage......if however when the water was 'forced' to the last rad i doubt it's the pump.....my guess is it needs balacing or it's airlocked. Try opening the filling loop as you drain from each cold rad in turn to push any air out.....

OK, this is my final plea with as much information as I have to see if anyone has any solutions/ideas before British Gas come down on Friday.

Further to all of the above, the heating suddenly started working this afternoon, right as rain and I hadn't done anything other than turn it onto timer (rather than continuous with just the one radiator nearest the boiler getting hot as before). This lasted for an hour before all other radiators gradually got cold. By turning the boiler on and off several times, it got a second wind and fired up all the radiators boiling hot for another hour, before returning to the status quo which is:

1) Radiator nearest the boiler boiling hot, all others stone cold.
2) Hot water on demand as usual (combi boiler) but gets SCALDING hot like never before.
3) Boiler constantly fires up for 8 seconds and then rests for 20.

When it's like this, I can 'push' the heat to the farthest radiator by turning each one off in turn using the TRVs but it always floods back to where it started and I'm reluctant to try balancing since it sprang into life (albeit for 2 hours) this evening.

I know that it's a long shot, but with so many of you out there has anyone ever experienced anything like this before?