central heating

please help have been having a problem with inconsistant heat from radiators (mainly lukewarm) which progressed to only upstairs getting hot unless you turn them both off then downstairs gets warm. Have tried bleeding all rads but no air ever comes out tried bleeding pump in airing cupboard now no radiators get any heat at all pump is spinning on all 3 speeds & hot water is ok can any body help?

New or old heating system , new or old problem? Could be sludge or air lock. Couldd still be a pump - rotors can fall off.

thanks for reply
its a new problem although heating has never been particularly hot
last night checked c/h loft tank was slightly low so topped up,checked pump
for air none found but it is spinning & pipes feel hot either side,tried moving lever to man on divertor valve pipes feel hot either side tried bleeding rads again & adjusting lockshield valves.
none of above has made system work bathroom rad got slightly warm although inlet pipe was hot,other rads did nothing,boiler now makes strange hissing/boiling sound when heating up but hot water is hot & plenty of it.
could it be sludge in pipes or boiler heat exchanger,or could the pump be spinning but not pumping water as it runs continually with either heating on or hot water on

sounds like the pump to me m8 check it out and let us know

Sludge knackers pumps over a period, so change the pump anyway, and go from there.