Go to a heating and plumbing merchant. Get a replacement, they will advise..
Then straight swap.
"Simon" wrote in message
...
Hello -

My central heating pump system is making loud rumbling noises when it
runs.
It's a Grundfos 18-60, which doesn't seem to be made anymore. Can anyone
suggest a direct replacement that is no larger externally, as the location
is quite cramped.

Is replacement just a case of switching off the power, closing the 2
isolating valves (assuming they haven't seized), and swapping the pump?

Thanks.