Will a system work partially on gravity with faulty pump

I know I've had other posts about my system but this is a fairly straight question.

If a pump is slowing down or not working will the CH and DHW either work or partially work as though on a gravity system or would the rads fail to heat at all.

I'm seriously thinking of getting a new pump tomorrow for the noises and performance I've got and don't know how to flow test mine.

All rads heat at top only apart from first 2 now I've opened the lockshields. The rest are wall ornaments.

will the CH and DHW either work or partially work as though on a gravity system

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In my exp, the hw might a bit if you're lucky, but not the CH beyond the first rad top.
You know they often have a screwdriver slot in the end of the shaft under the screw..... I wonder... electric drill and screwdriver bit...!

Will try a drill and driver bit in it tomorrow and see what happens.

As I said 2 rads are hot and the rest have hot tops only apart from the end 2 which are cold. Can't even open the lockshields any more.

I know 50 quid is 50 quid but think a new pump would be a good thing to try.