My Range Rover is Mumbling again

Hi Folks

My 89 EFi SE Vogue Auto is Moaning again, I'm thinking my water pump is shot.

On short trips nothing Temp doesn't move on longer trips 20+miles the temp goes up even though air con has been removed so no second rad. Rad, fan are ok and the head gaskets have been replaced.

Anyone with more experience of these than me can you enlighten me could it be the water pump ?

Does the same with Thermostat in or out I'm also thinking maybe the rad filler plug or expansion tank plug's need replacing

Charlotte, do in the following order and you 'may' save some $$$$.
A radiator and engine block flush to remove any soft deposits, a sulphamic acid diluted solution for 2 days to remove stubborn deposits, do the flush first - if still the same then the water pump or perhaps a leaking head gasket (Hot gases into the cooling passages, when the temperature rises does the reservoir cap vent out the overflow tube ?, also can you see any bubbles with the cap off - combustion gases - careful when removing the cap !!).
Cheers, roger.