How do i fix this problem ?

I have my central heating and water on timed, but last night decided to turn the central heating off and just let the hot water come on this morning. What a noise, so loud thought the house was falling down!! The pump sounds as if it is stuck 9but its not have checked), although it is new pump only 4 weeks old. Checked in the loft and there was a lot of steam and condensation from the tank and expansaion tank. The water from the taps is red hot also. I have tried to bleed the pump but no water flowing through it only lot of steam and the pump itself is very very hot. Tried turning the heating on to see if this was problem, but thats not coming on either now. Any ideas???