radiators

[hel123]

my upstairs radiator is only hot on the bottom corner. i can't bleed radiators as the have no holes like most radiators to air them. someone suggested behind my combi is a black knob and was told to turn it until the bar counter on my combi goes up, then turn it back. which i have done but still the same cold radiator. Has anyone else had this problem or can anyone help me please.

[stanleyman]

Presumably you have other radiators working ok so it must either be air or a stuck valve. All rads have provision for venting either on the top ends or at the top back. If this is ok and you have thermostatic rad valves this might be set too low or the pin or seat is stuck from being closed too long. If the system was allowed to lose pressure then there maybe an airlock in the pipes. Turn off all other rads to force water through to the cold rad.

[KARL]

There is at least one make of radiators that have their vents by the top edge and at the back of the radiator (i.e. facing the wall) rather than at the end as with the majority. Maybe this is what is installed in your house. Without a vent it is impossible to fill the thing unless the pipes happen to be connected at the top.