Stewart Devereux wrote:

Probably see from the time of the message just been woken up by the
expansion tank overflowing from the loft- sorted the blocked- the pipe that
is curved that runs in from the top missed the tank-assume this is a safety
overheating pipe-boiling water was running from it-Why?? Radiator red hot.
Emptied some hot from the tank(its a soild fuel boiler, left on over night,
water stopped, then turned rads on by moving down the therm on the tank and
more boiling water from the pipe. HELP. Surely pump is working-why did water
get so hot as to enter the expansion tank? therm seem to work, but was set
high-did it just
sticks or did the tank just get too hot, and the radiator were unable to
cope with the heat, so forced water out. When I turned pump on manually
boiling water pumped into expansion tank and help advice appreciated.


--
most likely problem is pump.
make sure pump is running by putting your ear to it and perhaps change
the speed with the switch on the side of the pump to ensure its
running. It is quite audible when running.
hot water would expand into the vent pipe by convection even if all
else failed.
Thats the reason for the expansion pipe ie to release pressure when
the system overheats.