Hi
The build-up of crystals on a waterpump is quite normal on an R4. Especially, in damper climates. This does not necessarily mean a leak. They can build up over the winter. If you are losing antifreeze/coolant you obviously have a leak/or the car is overheating (check the expansion bottle level if you cannot see an obvious leak, is the level of the antifreeze/coolant going down?). I notice you have the original factory clips on the two heater hoses. This means they must have been on there for at least 40 years! They lose their tension over time. Check you are not losing antifreeze from these two hoses. If so, change the clips for good quality hose clips. The only reasons to change the water pump are if the bearing is worn in the pump: check for play/listen out for a whirring bearing noise (or the pump has seized up) or the internal seal within the pump has perished (if the seal has perished, antifreeze/coolant will leak from an oriface which is tucked away under the front of the pump, you would need to feel for it with your hand and if your hand gets wet or you can see a trickle of fluid running down the middle of the pump and collecting in the central recess of the gearbox bell housing, suspect a perished seal.
A leak can also occur due to a perished water pump gasket which would mean taking the pump off in any case in order to change the gasket. If the pump is relatively new (has no play in the bearing and does not have a perished seal), I would change just the gasket. If the pump has been on there for donkeys years, it would make sense to change it rather than put the old one back (as your heater hoses have the original clips, I suspect your pump has been on the vehicle since it rolled off the production line).
