advice with heating problem

[littleh]

Hi, can anyone help. I have a central heating system which appears quite old, I think it is a system boiler heating system.
It has a presurised expansion tank and has a gas boiler.It also has motorised valves on the system.
a few days ago there were loud rattling coming from the pump and although the boiler had its pilot light on there was neither water or CH.
The pump then cut off altogether. I tapped it quite hard and it appeared to rattle into action, then went dead after a short time, 10 mins.
I checked this site and from other posts i thought the pump was faulty.
I changed grom a WSP Gold to a grundfos 15/60.
Guess what it started to make a quieter rattling and the CH and Water is still not working. although after replacing the pump the boiler fired up for a min or two, then went back to pilot only.
The pipe from boiler to pump is hot and it gets cooler from pump onwards.
The pipe going up to expansion tank is very hot.
Any advice would be great. :lol:

[Perry525]

The pump would be fitted on the cold side of the boiler!
Try turning it over.

[littleh]

Thanks for replying, sorry dont know what you meant, the pump was replaced at exacly the same spot where it has been probably since installation.
I suspect actuater problems but cannot move them by hand and dont know how to check whether they are working or not.

[htg engineer]

possibly a fault with the three port valve/ actuator, it may be stuck in mid position and this would cause a rattling noise as the water would be pumped against it. Remove the actuator/motorised valve and turn the spindle by hand. Then turn the heating on and see if the actuator moves and if the heating comes on.

check you have put the new pump in the right way

[littleh]

Thanks for your advice. Ive just got a second opinion from a heating engineer who suggests that i replace valves and actuator.
I will try that and hope it works.